and I will give it to you. My mother says that Odysseus is my father.
I don't know this myself. No one witnesses his own begetting."
Prior to the days of DNA testing, it was basically impossible to verify a child's paternity. The only evidence:
- the word of the mother, who might be lying, or might not know herself (the subtrope Who's Your Daddy?)
- stark differences or great similarities in skin, hair and eye colour (like a Chocolate Baby) or other forms of Uncanny Family Resemblance
All this trouble is embedded in such proverbs as "It's a wise child who knows his own father", and "Mama's baby, Papa's maybe".
This can be a source of tension and drama even when the mother is honest because neither the child nor the father can prove it. The Green-Eyed Monster is very prone to doubt. It can also complicate the Heir Club for Men, as the man usually wants his heir to be his biological descendant. If the mother refuses to tell, only men who have actually slept with her can even guess, and speculation tends to run wild. If she lies, the man has no way to prove his innocence unless he has an alibi that would preclude his having slept with her — merely knowing he had not is not proof — and he may even be forced into a Shotgun Wedding. If the man believes himself to be sterile, and the Law of Inverse Fertility works, expect the resulting arguments to be ugly.
Doubling up this is the fact that the legal rule is often Mater semper certa est, pater est, quem nuptiae demonstrant: "The mother is certain, and the father is him to whom marriage points." A man who suspects his wife's child is not his has no legal recourse; he is the legal father. However, this is usually a rebuttable presumption now (i.e. this can be proven otherwise with DNA evidence).
A powerful force behind My Girl Is Not a Slut and Nature Adores a Virgin in Real Life, because exclusive sexual access to "his" woman used to be the only way for a man to be sure that her children were also his. To what extent there is reason to doubt in real life is not known; numerous urban legends claim a high percentage of babies are attributed to false fathers, but the location of the studies determining this tends to migrate a lot.
A trope limited to historical settings (1980s or earlier) nowadays, as Daddy DNA Test is the Trope Breaker. (Unless the potential father is one of a pair of identical twins or clones, or testing is impossible for some reason.) Compare Not Actually His Child.
- A major plot point in Assassin's Pride. There were enough witnesses that everyone is fairly confident that the female lead, Melida, wasn't Switched at Birth, but they are far less confident that she is Duke Felgus's daughter since most people believe a Muggle Born of Mages to be impossible for a ducal house. It is widely agreed that it is far more likely that her wealthy but commoner mother had an affair with another commoner. Since Melida's mother, Melnoa, passed away some time ago, she is no longer available for anyone to ask, leaving Melida's family stuck investigating all of Melnoa's male friends and deciding whether or not to give up and kill Melida.
- Played for drama in Berserk after the eclipse. Casca goes into labor and gives birth to a premature but demonic hell baby. Guts at first believes the baby to be Griffith's, who had previously became a demon lord and raped Casca to insanity and begins panicking over the possibility. The Skull Knight confirms that Guts is the father saying that Casca was impregnated by him roughly a month before the Eclipse. However, the baby was nonetheless tainted and deformed due to the rape. The news did not make Guts very happy either way.
- In A Cruel God Reigns, Greg believes his first wife, Lilya, cheated on him and that Matt is not his son. Unfortunately, it is never definitively proven either way.
- In Fruits Basket, while a young Tohru is at her father's funeral, some relatives speculate that Katsuya Honda wasn't really her father, and that her mother Kyouko just had an affair. To her face. Their only "evidence" for this was that Tohru didn't particularly resemble Katsuya and that Kyouko had, years and years ago, been in a biker gang. Hearing this spurs Tohru to begin to speak very formally (something Katsuya was well-known for doing), to try to convince others that he really was her dad.
- I'm the Evil Lord of an Intergalactic Empire: The story starts with Liam on his death bed having been worked to the bone by several Evil Debt Collector due to debts forced upon him by his ex-wife which include child support for a daughter that's most likely the result of her cheating on him. The whole thing gives Liam Paralyzing Fear of Sexuality and a chip on his shoulder in his next life.
- Discussed in Kaguya-sama: Love Is War. Kaguya's father admits on his deathbed that the reason why he always been so distant with her is because she wasn't sure if she was actually his biological child (seeing as Kaguya's mother was a prostitute). While he could have very easily taken a DNA test (given that the story takes place in the late 2010s), he avoided doing so out of fear of how he would react if the test came back negative.
- Mars (1996): Rei and Sei are legally Takayuki's children, but everyone except the kids themselves knows they're actually his brother Akihiko's.
- Inverted on the Naruto Gaiden sequel mini-series with Sasuke's daughter, Sarada. She greatly resembles her father plus glasses, but when she asks her mother Sakura (who doesn't wear glasses) if her father wore glasses too (he doesn't), she acts very evasively of the question. Sarada then questions her mother of even being married to her father; logically, Sakura doesn't take it very well and has a rage-fit, allowing Sarada to discover a picture of Karin (who does wear glasses) with her father. And then it turns out that Sakura is Sarada's biological mother; the supposed "evidence" saying that Karin was the girl's mom was actually badly-handled by Karin's friend Suigetsu since Karin was Sakura's midwife and some DNA of both women got mixed up. The evidence was actually Sarada's dried umbilical cord, which Sakura gave to Karin as a gift for delivering Sarada. Suigetsu mistakenly THOUGHT the umbilical cord came from Karin. The cord's DNA matched with Sarada's because it came from Sakura.
- The female shogun Yoshimune from Ooku invokes this trope in pondering what a patriarchal Japan would look like. She thinks that matriarchy has a distinct advantage because of it. This may influence Yoshimune's later choices in how to handle her Royal Harem: she spends equal time each week with her primary male concubines, interspersed with one-night-stands with servants. Thus, when she becomes pregnant, none of them can argue when she names the most malleable candidate as the father.
- In Red River (1995) Lady Güzel, a princess who had once been Kail's lover, insists that he's the father of her child. Because Kail's inline for the throne and having an heir would be beneficial to him, there is a lot of pressure for him to accept the child as his own... but Kail himself knows that it's impossible that he's the boy's father, because he and Güzel haven't seen each other for years. It turns out Güzel had been brainwashed by Kail's Wicked Stepmother Nakia into lying about her child's parentage. Upon being woken up, she readily admits that the father was a Wandering Minstrel and that the idea that Kail was the father was preposterous.
- Also, Nakia finds herself in such a situation later. As she loses power, people begin to gossip more and more openly about how they think her son Juda is actually Urhi's son with her; the fact that Juda and Urhi have exactly the same hair color and that Urhi is the person closest to Nakia really don't help matters. It turns out Juda really is the king's legitimate son: Urhi is a eunuch and was castrated quite a while before he even met Nakia.
- In one story of Tomie, the baby of a family grows up to be a creepy child version of Tomie, who naturally resembles and acts like no one in the family. The father accuses the mother of having an affair because of this, especially when he finds out that a wealthier family apparently has a child who looks the same. The mother, meanwhile, maintains that the child is his and that she did look like him when she was an infant. Actually, there are several child Tomie's running around because a creepy guy injected the babies with Tomie's blood.
- In Yume no Shizuku, Kin no Torikago, Hurrem frequently sleeps with Suleiman as his concubine, but ends up sleeping with Ibrahim once. When the news of her pregnancy becomes known, Hurrem and Ibrahim separately wonder if the baby's father is Ibrahim or Suleiman. Nothing is stated outright, though Ibrahim's worry remains for a long time.
- In the Child Ballad Gil Brenton, the hero accepts the heroine's story of how he got her pregnant, but the ballad ends with magical writing on the baby's body affirming that he is in fact the father, to doubly avert this trope.
- The Basque ballad Pello Joxepe tells of a man refusing to acknowledge his son as such.
- The Song of Dermot and the Earl, an Irish poem in Anglo-Norman, mentions offhand of one family: Li un ert fiz, li altre pere, Solum le dit de la mere. ("The one was son, the other father; according to the word of the mother.")
- "Johnny Be Fair" is a joke that got turned into an Irish ballad. Buffy Saint-Maire and Debra Cowan both sang versions of it. The song tells of a girl who wants to marry, but all of the young men who propose to her turn out to be her father's bastard sons. In the end, she goes to her mother in despair, and her mother sets her straight:
My mother said "If your father knew,It's me he'd surely kill,For your father's not your father,So marry whom you will."
- The Flintstones: Monogamy is a relatively new concept in this comic and one of its defenders says it serves to end doubts on fathers' identities.
- Played with in The Pulse, when Danny Rand (Iron Fist) accuses Jessica Jones of lying about being pregnant with Luke Cage's baby. Misty Knight quickly puts him in his place.
- In Robin, after asking Oracle for advice about Stephanie's pregnancy, Robin quickly denies his paternity is even possible — "Not guilty. Not even a suspect." Downplayed in that Oracle accepts his word for it.
- In Savage Dragon, Dragon's then-girlfriend was pregnant. Since she was a past prostitute and there was a subplot at the time indicating that she might've been cheating on him (she wasn't), the first words out of his mouth were "Is it mine?", which upset her a great deal. He ended up apologizing, she ended up forgiving him, and the baby ended up being his, leading to the boy becoming a hero years down the line.
- In Spider-Man, when Peter learns that his deceased lover Gwen Stacy had twin children who have reached adulthood in less than a decade, he soon realises that the children believe him to be their father, but is able to confirm that this can't be the case; downplayed with the revelation that Mary Jane actually knew about the children long before Peter did and never mentioned it to avoid tarnishing Gwen's memory.
- In Watchmen, Laurie is aware that her mother's husband is not her father, but her guess at the actual father is off, and when she finally realizes the truth, she's shocked and horrified.
- In The Brown Bear of the Green Glen, the woman John leaves pregnant comes to track him down with magic.
- In The False Prince and the True, a youth on trial for striking the prince reveals that he is actually the king's son from a secret marriage, whereas the prince is actually a quarryman's son, passed off as the king and queen's because the queen feared the king's wrath.
- In The King of Erin and the Queen of the Lonesome Island, the queen of Tubber Tintye finds herself with child, and has to hunt around to find out who the father is. When she tracks down the father, she forces the knowledge from the queen of Erin that her sons were in fact the sons of the gardener and the brewer.
- In Peter the Fool, the king goes to investigate how the princess came to be pregnant. The baby recognizes the man responsible—by wishing her to be pregnant.
- In the folktale The Snow Child, the husband claims to be taken in by the fantastical story his wife tells about how the child came to be conceived without a father, always involving snow. Then, later, he sells the boy as a slave and tells his mother that he melted.
- In The Goblin Emperor fanfic The Honourable Thing, this is played with. Beshelar knows for certain that the child is not his, as the married the mother to save her reputation. He constantly has to dispel other characters' suspicions.
- Downplayed in In the Bleak Midwinter; the wealthy Riddles, and especially their maid Fiona, are naturally a bit suspicious of a girl who comes to their home and presents a baby who she claims is Tom's. Since Hermione isn't trying to extort anything from them, however, just giving them the entirely voluntary option of raising their son and grandson, they soon warm to her. It also helps that little Tommy shares his father's unusual eye colour.
- In later chapters of the NCIS Doorstopper Shards To a Whole, Tim and Abby McGee and Jimmy and Breena Palmer are happily living in a four-way relationship together. When Breena is pregnant with her youngest child, the ultrasound photos strongly indicate that the baby more closely resembles Tim than Jimmy. After the initial discovery, the trope is largely averted since, as far as the McPalmers are concerned, any child born into their family (including those born before the four of them hooked up) belongs to all of them and Jimmy and Abby feel zero jealousy at the thought of Breena carrying Tim's baby.
- Persephone: Despite being married to Snotlout, it is mentioned that Ruffnut cheats on him, making it likely that her child might not actually be his. Later averted.
- In The Queen of Sunshine and Bright Things, Maleficent mentions to herself that Elsa's powers are likely due to her mother cheating with a fairy. She doesn't dare bring up her thoughts to Elsa herself.
- Retrograde Motion: This is actually weaponized by Barbara for the de-aged Jason's cover story. Once it becomes clear they can no longer keep Jason cooped in the Manor, Barbara arranges an article to published in the paper that suggests Jason is Dick's possible lovechild with Artemis, so that way they have a reason to keep him near. The plan is to continue the charade until Jason is turned back to normal and then have the Daddy DNA Test provide a negative so they can sweep it under the rug. When the transformation turns out to be permanent, however, Dick and Artemis end up legally (if falsely) becoming Jason's biological parents in order to raise him.
- Occurs in Stars from Home when Chris Summers marries a very pregnant Katherine. Notably, Chris is certain it's his, but his friends and neighbors are not.
- Briefly discussed and defied in the Fruits Basket fic Unshakable. When Akito reveals her pregnancy, Shigure has no doubt in his mind that the baby is his, but also recalls that Akito also tended to spite him by sleeping with Kureno. Already knowing what Shigure is thinking, Akito confirms that she's pregnant with his child, stating that she's "not like that anymore."
- The Victors Project: Abram Mills (Victor of the Sixty-Ninth Hunger Games), is the son of widowed chocolatier Caramel Mills. While officially Abram is the son of her deceased husband, Ben Cooper (Victor of the Twenty-Ninth Hunger Games) had a drunken one-night stand with her around the time of Abram's conception, meaning there's a possibility Abram is his biological son, even though they look nothing alike. Ultimately, this possibility is enough for Ben to come out of retirement and mentor Abram for his Games.
- In Who Needs Genetics When We Have Family?, Ruby and Yang learn that their father Taiyang was in a relationship with both their mother Summer and uncle Qrow. However, it's unclear which sired Ruby, because Ruby takes after Summer so much.
- Wishing Well: None of the stallions in Ponyville will admit to being the father of Cotton Candy's daughter Pinkie Pie, so there's much rumor on who it could be.
- In Craving the Sky, Weiss is born a faunus and immediately assumed to be a bastard despite Willow's insistence that she didn't cheat. Weiss does bear a strong resemblance to Jacques otherwise, but unfortunately the daddy DNA tests keep turning out inconclusive.
- In the Avatar: The Last Airbender fanfic rumor has it, "everybody knows" that Zuko is actually Iroh's son after he had an affair with his brother's wife. This surprisingly doesn't cause any problems for Zuko, since Ozai was such a bastard and Iroh such a beloved hero. Most of the Fire Nation (and certainly the rest of the world) pretty much just shrugs and says "that makes sense, good thing we got Zuko instead of Azula." The fic is mostly vignettes of random people's opinion on this "fact," from minor soldiers to nobles to a bastard girl who is being bullied for her status. Iroh's own thoughts imply none of this is true, but he doesn't see a need to make an issue of it.
- The Mountain and the Wolf: The Wolf offhandedly mentions three Chaos tribesmen from the local equivalents of Scandinavia, Central Asia, and the Far East competing for the hand of a woman who'd slept with all three. The baby was born with red, black, and brown hair. Not exactly how genetics work, but when Chaos is involved...
Three warriors, each claiming to have gotten the chieftain's daughter pregnant and demanding her as their bride. You can imagine their faces when the child was born, with hair all at once red as a Norscan's, black as a Hung's and brown as a Kurgan's. Yongvar Three-Fathers, his name is. Very touchy about the subject. Collects the lips of those who would mock him for it.
- 13 Minutes: It's left unclear if Elsa's son was sired by Elser or her husband, as she had been with him in the period before the baby's conception. This is not much of an issue though, since the baby boy dies shortly after birth, and her husband never knows about the affair.
- A Wedding (1978): Buffy claims that she's pregnant and Dino is the father, but it turns out that she slept with almost everyone at the Military School, so Dino probably isn't the father.
- Backstreet Dreams: Lucy slept with other men right up until she married Dean. After Shane is diagnosed with autism, Dean wonders if he's even his.
- This trope is averted/inverted in Dodes'ka-den by Akira Kurosawa with a local woman who has five children. The children tearfully ask their mother's husband, their alleged father, about the rumors saying they're not his children; he tells them he is if they say he is.
- Olive from Drive, He Said is married to Richard and having an affair with Hector. When she gets pregnant, she thinks the father is Hector, but she doesn't know for sure.
- In Genghis Khan, Genghis's wife Bortai is kidnapped by a rival. She comes back pregnant. Genghis insists on recognizing the boy as his own son. This happens in another Genghis Khan biopic, Mongol—mainly because it happened in Real Life. The dubious parentage of Genghis's first son, Jochi, cost Jochi a shot at succeeding his father and played a significant part in the fracturing of the Mongol Empire.
- It's left ambiguous in Joker (2019) whether Arthur's father is Thomas Wayne or not. It's revealed his mother was delusional and adopted Arthur, but this is called into question by two Freeze-Frame Bonus' showing that Arthur's mother has something addressed by "T.W." and her papers saying she had a lobotomy. It's possible that Thomas covered up his affair and faked adoption papers.
- In Mamma Mia! the whole plot center's on confusion over which one of three of Donna's former lovers is Sophie's father.
- In Mohawk, Oak has two lovers—a Mohawk warrior named Calvin and a British soldier named Joshua—one of whom is the father of her unborn child, but Oak does not know which.
- In The Nativity Story, the audience knows that Mary is telling the truth when she says that God is the father of her unborn child, but Joseph and her parents are a bit more skeptical. Joseph eventually believes her after the Holy Spirit visits him in a dream to confirm her claim, and goes on to publicly claim the child as his, so it would have a father on Earth.
- The Painted Veil (2006): "Am I the father?" "I don't know."
- The Scarlet Empress: It's very heavily implied that Tsar Peter III is not the father of his wife Catherine's baby (Catherine being the future Catherine the Great). Peter and Catherine hate each other and are never in each other's company. The scene where the child (the future Paul I) is born comes immediately after the scene where Catherine has sex with a random guard. Later, a smirking Peter refers to the baby as "an unexpected addition to the family."
- West of Zanzibar: Lon Chaney plays a man whose wife was going to run away with another man and then died shortly after childbirth. He raises his "daughter" to be an alcoholic prostitute. Then the other man shows up, and tells him that his wife never went away with him—the child is his own.
- Inverted in this Dumb Blonde joke:
The blonde discovers she's pregnant and goes to confront her husband: "Are you sure it is mine?"
- A pregnant woman complains that her husband keeps minimizing the discomfort and pain of childbirth until the doctor explains that they have a machine that will transmit all the sensations to the father. They do so right through the delivery but the husband shrugs it off saying it doesn't hurt at all. They started the machine at setting #1 and kept increasing it until it was at #10 but he felt nothing. They return home with the baby to find out that their mailman had dropped dead right on their street.
- A boy lucked out on a phrase that got him anything he wanted - "I know your secret". Having gotten a new bike from his dad and new baseball mitt from his mom, he decided to try it out on the milkman... who swiftly embraced the boy shouting "Son!"
- A young man keeps meeting young women and wanting to marry them, only to have his father confess to being unfaithful and the woman being the young man's sister. Finally, despairing, he confesses to his mother, who tells him that while his father was being so unfaithful, she got lonely, meaning that he could marry any of them. (Lots of variations, including some where it's a young woman who wants to marry.)
- A middle-aged couple had two beautiful daughters but always talked about having a son. They decided to try one last time for the son they always wanted. The wife got pregnant and delivered a healthy baby boy. The joyful father rushed to the nursery to see his new son. He was horrified at the ugliest child he had ever seen. He told his wife "There's no way I could be the father of this baby. Have you been fooling around behind my back?" The wife smiled sweetly and replied: "No, not this time."
- A variation is about an elderly couple who has had 8 (sometimes 12 or 13) children: all of them brown-haired except for one lone redhead. The wife is on her deathbed and calls for her husband, for she wants to confess something to him. The husband comes, and tell her that he assumes it's about the redheaded boy he always suspected wasn't his. "Oh no!" the wife says "That one is yours, it's about the others."
- A farmer's son had, after his tradition, asked his father for permission to marry one particular girl. When the father heard the name of this girl, he made it clear that he didn't want his son to marry her, because it turned out he was her father. This shocked the son, and he went straight to his mother with the problem. The mother scoffed and said: "Just marry the girl, son. You see: my husband is not your father."
- There is a joke when a paternity case is brought to the court, but the suspected father refuses to provide a DNA sample, so his parents submit theirs. It tests positive... but only for the granny.
- An impoverished aristocrat resigns himself to organizing guided tours of his ancestral castle. One day, he notices one of the tourists bears a striking resemblance to himself. He goes up to him and asks "I can't help but notice you look very similar... Did your parents work here by any chance?" "Yes, they did." "Ah, yes, my father was something of a skirt-chaser... Your mother was a chambermaid, no doubt?" "No, I never knew my mother, but my father was a stablehand."
- A variant of the above joke dates back to ancient Rome.
Augustus: Was your mother ever in Rome?
His provincial lookalike: No, but my father often was.
- What's the sorrow of the baron's stablehand? "My father is a baron, my son is a baron, and yet I have to work in these stinky stables!"
- A king has three sons, but while two of them are strong, handsome and brave, the third is sickly, weak, plain and timid. The king is tormented by the thought that his wife may have cheated on him throughout his entire life, until finally, on his deathbed, he has the queen brought to him. "My love," he says, "I am old now, and dying, and can forgive almost any sin against me. But there is one I could not. But I must know. My third son. So unlike the other two. Is he truly mine?" To which the queen responds, "My love, I could never lie to you on your deathbed. So believe me when I promise you that you are the father of our third son." Finally satisfied, the king breathes his last... and as soon as he has, the queen sighs in relief and says: "Thank Christ he didn't ask about the other two."
- A Dumb Blonde gives birth to a Chocolate Baby. Before the husband can recover from his surprise, she spits venomously at him, "I knew you were sleeping with that black woman down the street!"
- Ascendance of a Bookworm: Inverted in Ferdinand's case. One of the few facts about his mother that the story has cared to deliver is an antagonist claiming that nobody is sure which of Ferdinand's nobleman father's mistresses gave birth to him. There is also a chapter from Ferdiand's point of view that mentions that his mother couldn't be relied upon to protect him from his Wicked Stepmother (his father's wife) and another chapter from his cousin's point of view mentions she offered him no protection whatoever. It's hence unclear whether the antagonist was exaggerating the uncertainity of the identity or if it is uncertain because none of the candidates came to his help in his time of need. Things are further complicated by the fact that in the story's setting, it's perfectly normal for nobles to hide a child's existence from the public up to their seventh birthday and that guardianship shenanigans frequently happen during the first seven years of a child's life.
- Aunt Dimity: This figures in the Backstory of Kit Smith, but it isn't revealed until many years after the fact. The truth his father was neighbour and family friend Christopher DuCaral is actually something of a relief, since Kit thought insanity ran in his genetic heritage and refused to marry anyone to avoid passing it on. On confirming the news, he goes to his long-time love Nell Harris, helps her down from her horse at the riding school, and kisses her.
- Bazil Broketail: King Sanker of Marneri doesn't believe Besita is his daughter, since her mother had numerous affairs (which he had her executed for). He hates Besita as a result, and kept her from ever marrying because her children might become pretenders.
- In Edgar Rice Burroughs's Beyond Thirty, the British Isles have "retrogressed"—there are tribes that did not have a word for father, and other tribes where they are aware of fatherhood, but practice matrilineality because of this trope. The heroine tells the hero not who her father is, but whom her mother once told her was her father.
It appears that the line of descent is through the women. A man is merely head of his wife's family—that is all. If she chances to be the oldest female member of the "royal" house, he is king. Very naively the girl explained that there was seldom any doubt as to whom a child's mother was.
- In The Barrakee Mystery, the first Bony novel, the Aboriginal girl Nellie Wanting is the daughter of a woman who has been in relationships with several different men. Nellie's mother claims her father was an Aboriginal man known as "King Henry", but some other members of the tribe say they doubt it. It's never established who Nellie's father was, but it can be assumed that it wasn't King Henry because the author pairs her romantically with a man who turns out to be one of King Henry's sons.
- In Brideshead Revisited, Charles's wife has an affair and conceives a child. While it is not clear who the baby's father is, Charles's insistence on referring to it as his wife's baby suggests that he does not think it is his.
- In A Brother's Price men are so rare that a husband can usually be sure it's his, and the mothers who get pregnant via visiting a "crib" have an interest in truthfully documenting fatherhood, to avoid inbreeding in the future. However, there are rumours about a neighbour family, namely that the younger children were not actually fathered by the frail and feeble father of the family, but the son.
- In Leo Frankowski's Conrad Stargard series, one of Stargard's men finds himself suddenly married to a beautiful employee at the boss's factory, but when she quickly becomes pregnant he ponders this trope, wondering if he's been manipulated into saving a former mistress some embarrassment.
- Played for Drama in A Cry in the Night. Jenny starts to get the impression that Erich believes her new baby was actually fathered by her ex-husband, especially given that during the birth he expresses dismay over the baby's hair color (it's much darker than his). Even when the baby's hair begins to lighten to his color, he remains emotionally distant and doesn't let the baby be named after him despite it being a family tradition for the Kruegers. It ends being Played for Horror given it's implied Erich murdered the baby out of deluded belief he wasn't the father.
- In I Shall Wear Midnight, Tiffany's father attributes the abusive Mr. Petty's anger towards Amber (without excusing it) to this trope.
- In Wyrd Sisters, it's revealed at the end that the Fool is Tomjon's half-brother, and when Tomjon rejects the crown, he is made king. It is then further revealed that their shared father is not the late king, but the late fool.
- In Marie de France's Le Fresne, a woman taunts another woman with infidelity after she bears twins; then she bears twins herself, and unable to prove her innocence, exposes one daughter.
- In Gods and Warriors, this was invoked by Pirra's mother, High Priestess Yassassara, when she decided to bear a child; she mated with three different priests so that none of them could claim to be the father. They all died in an earthquake when Pirra was little, or so she was told; she wonders if Yassassara got rid of them so that they wouldn't cause trouble.
- Discussed multiple times in The Good Soldier vejk by Jaroslav Hasek, both for humans and dogs (Svejk was selling dogs before he got drafted). Since it's set in 1914, there are no reliable tests, and some characters (Svejk included) believe that a child can have multiple fathers. The funniest example is Svejk's story about a prostitute, who gave birth to non-identical twins with a rather unusual set of birthmarks, eye and hair colours and minor deformities. She sued 16 clients for child support (8 per son) but lost all suits. Svejk comments that she should've picked a single one and hired witnesses to confirm him frequently visiting her.
- In Robin McKinley's The Hero and the Crown, downplayed. Aerin reflects that the only evidence that her father is that his wife gave birth to her — though no one says so, because her mother's character is well-known.
- Becomes an issue for two characters in Larry Niven's The Integral Trees and The Smoke Ring. After one female character is used as a Sex Slave, her husband can't accept her child as his until learning that the child inherited a respiratory problem from Mom's husband/his true father.
- Julie Kagawa's The Iron Fey: Meghan learns (in The Iron King) that her mother's husband, who vanished when she was six, was not her father. Her biological father is actually Oberon, king of the Faerie Summer Court (and he knew about the pregnancy, sending Puck to watch over her).
- In Jane Eyre, Mr. Rochester's ward is the daughter of his one-time mistress, who sent him the baby after he had dismissed her when he learned she was unfaithful to him. She said the child was his; he assures Jane he has his doubts. Jane herself doesn't see a drop of family resemblance between them.
- In Andre Norton's The Jargoon Pard, Kethan is his uncle's heir because as his sister's son, he is his most reliable kin. Of course it turns out that Kethan's mother isn't his mother at all so there goes that theory.
- In Sharon Shinn's Jenna Starborn, a retelling of Jane Eyre, Everett Ravenbeck also has a ward of unknown paternity born to an erstwhile mistress—he tells the title character that he never had the child DNA-tested, much to her surprise.
- The Jungle has, as part of Jurgis's Trauma Conga Line, his wife Ona tells him that she was raped by a businessman and she's been going to him for conjugal visits to ensure financial security for the family and also that she is pregnant. From what is narrated of their miserable bedtime experiences, they are most likely not having sex and if they are, then it is not very often. Therefore, there is the chance that Ona got pregnant from her visits with Connor. However, Jurgis never makes any comment on the paternity of the child.
- In Ladylord, the baby Sen-Ya is believed to be the long-desired son and heir of First Lord Yassai, but is not actually Yassai's son. Yassai is mostly impotent, and to get pregnant, the concubine who gave birth to Sen-Ya visited the dungeons as an anonymous lady of the court and had sex with one of the prisoners (as the guards seem to indicate ladies of the court not infrequently do). Yassai assumes that the second part of Sen-Ya's name is to honour him, but it's actually from the prisoner.
- The Last Dragon Chronicles: When Liz starts to explain all about Arthur, the first conclusion is that he is Lucy's father. Wrong. Liz quickens an egg, it hatches, Arthur comes home and she's nursing a newborn. His conclusion? She cheated.
- In Giovanni Guareschi's Little World of Don Camillo, Don Camillo asks Peppeno's wife if her baby is her husband's — and points out that their party approves of free love when they are indignant.
- In Dorothy L. Sayers' Lord Peter Wimsey novel Strong Poison, a servant talking about the infamous aunt and actress, says that her marriage was just a sham, and there's no knowing who the father of her two children were.
- In Madeleine L'Engle's The Love Letters, Charlotte fled to Portugal because when she told her husband she was pregnant, he had asked her who the father was. It was him.
- This is the backstory of one of the characters in Mercedes Lackey's Magic's Promise; when the kid was born early and looked like neither his mother nor his father but exactly like his maternal uncle, his father assumed the very worst, and took it out on both mother and child. Particularly awful because there was a way to check; the father just didn't want his suspicions confirmed. The boy was simply born prematurely, and wasn't the uncle's.
- In Poul Anderson's The Man Who Counts, one set of aliens holds another in contempt because they breed in a blind frenzy after their migration, and children's fathers are unknown. (The other set holds the first in contempt for breeding all the time, like fish.)
- In Marion Zimmer Bradley's The Mists of Avalon, Morgaine's narration mentions that the native Britons and the people of Avalon trace lineage and descent through the maternal line, since you can always be certain who gave birth to a child. This is a minor plot point later on when the King feels his firstborn son cannot be King after him since the child was born prematurely and people will be suspicious that he was conceived with the Queen's previous husband.
- In the Chivalric Romance Octavian, the emperor's wicked mother accuses his wife of infidelity and claims her twin children are not his.
- In The Odyssey, Telemachus wonders about this—a doubt that no one else expresses—because he wonders if he is a worthy son of such a father.
- In Ovid's Elegy XIII, he invokes Isis and Lucina to save his mistress, Corinna, after an attempted abortion; during the course of it, he admits that the child may not be his.
- There is a recurring reference in The Priory of the Orange Tree to the rumor that the late Queen Rosarian had an affair with the privateer Gian Harlowe. It's hard to confirm whose daughter Sabran is because Berethnet queens take so strongly after their mothers as to leave no trace of paternal resemblance, and it doesn't affect her rule because Inys is a queendom, but it is there nonetheless. As the book progresses and more about Rosarian's life is revealed, the probability that Sabran is Harlowe's daughter becomes stronger, and he implies a fatherly concern over her late in the novel, but it is never confirmed outright.
- In L. Jagi Lamplighter's Prospero's Daughter trilogy there is considerable speculation about Caliban's father. In the end, he has one question and uses it to confirm what the evidence points too.
- Mentioned in Anne Rice's The Queen of the Damned in relation to the Great Family that descends from Maharet, who had a daughter before being turned into a vampire. Maharet has spent millennia tracking and protecting her descendants. However, she only tracks the matrilineal descendants due to this trope, even in modern times when DNA testing can be done (the book was written in 1988).
- In Scavenger Alliance, Cage uses this idea to intimidate Blaze, claiming that Donnell doesn't believe she's his daughter because while her brother Seamus was the image of Donnell, Blaze herself looks nothing like him. In fact, Blaze is the image of her mother, and Donnell is baffled that anyone would suggest she's not his.
- In Angie Sage's Septimus Heap novel Magyk, Sally is convinced that this trope explains why Jenna doesn't look like her family. Fortunately. In reality, Jenna's a foundling, and they must hide her origin.
- George R. R. Martin's A Song of Ice and Fire:
- There is a succession struggle after the current king's death due to this trope (His wife Cersei having indulged in Twincest but nonetheless claiming the children are her husband's). Jon Arryn note and Ned Stark were both put onto it by the discovery that in past cases where Baratheons and Lannisters have had children together, the children always had black hair rather than the blond hair characteristic of House Lannister.
- Inverted with Jon Snow. His father, Lord Eddard Stark, raises and loves Jon alongside his true-born half-siblings at his home castle in Winterfell, openly presenting Jon as "his blood" which everyone assumes means his son. He provides him with a highborn upbringing but Jon has no idea who his mother is as it has not been revealed to Jon, most characters in the series, or to the readers. As a result, a number of characters have provided Wild Mass Guesses of their own but none of them line up with the fanon conjecture, and the sole character who can confirm any of these preductions — Howland Reed of Greywater Watch — has yet to appear "on-screen." No one in-universe doubts that Jon is Ned's son since the two share the "classic Stark" appearance and personality traits. Jon even looks more like Ned's son than his trueborn sons (who all inherited more of their mother Catelyn's features), which is one of the reasons Catelyn resented Jon so much. Out of universe there is a theory that he's actually Ned's nephew via his sister Lyanna Stark and Prince Rhaegar Targaryen, which is confirmed true in the TV adaptation Game of Thrones at least.
- Featured in Archmaester Gyldayn's Histories, with Rhaenyra's three eldest sons looking nothing like her (likely gay) first husband. Her detractors, the Greens, claim that the boys were fathered by Rhaenyra's lover Ser Harwin Strong. It's an inversion of the Baratheon/Lannister case, as two people with pale Valyrian coloring supposedly produced three dark-haired, dark-eyed children.
- It's also a key feature of the backstory of the Blackfyre pretenders. Daemon Blackfyre claims that the current king Daeron II wasn't the son of the previous King Aegon IV but of Aegon's brother Aemon; therefore, Daemon (the bastard-born but legally legitimized son of Aegon) was the rightful heir. The resulting civil war flared off-and-on for nearly a century. However, the general consensus is that Aegon himself started the rumors of Daeron's supposed illegitimacy out of spite, and to try to build a case for disinheriting him in favor of Daemon.
- Also during Aegon IV's reign, his cousin Elaena was married to the elderly Ossifer Plumm, who apparently died on their wedding night before or during their consummation (supposedly from the shock of her beauty). Nevertheless, Elaena had a son later on whom she claimed to be Ossifer's, but is widely suspected to have actually been another of Aegon's bastards (and leading to many jokes about how well-endowed Ossifer must have been to have fathered a child from six feet under).
- During the Dance of the Dragons the town of Tumbleton was taken by the Greens. The Green Ser Jon Roxton claimed Lord Footly's wife Lady Sharis as his prize and killed Footly when they protested. Later a son was born to Sharis who was claimed as Footly's heir but was likely Roxton's.
- Numerous fan theories revolve around this trope. They range from plausible, if unconfirmed (Petyr "Littlefinger" Baelish siring Lysa Arryn's only surviving child; the two did have an affair and Sweetrobin resembles Littlefinger somewhat), to wilder (Elia Martell had an affair with Arthur Dayne; there is little reason to believe this at all) and almost story-breaking (the "Tyrion Targaryen" theory which suggests Tyrion is a product of his mother's rape by the "Mad King" Aerys; considering Tyrion's official father is abusive, this would've been all too convenient for both Tyrion and his horrible father).
- In Gene Stratton-Porter's The Song of the Cardinal, with some Fridge Logic. The father cardinal suspects an egg was laid by an interloper and the mother knows it for her own. Except, of course, her actual egg could have been tipped out of the nest by a brood parasite—avian mothers would not have the certainty of a mammalian one.
- In some forms of the Chivalric Romance The Swan Children, a woman taunts another woman with infidelity because she had given birth to twins; later, she gives birth to seven children at once, and her mother-in-law taunts her with the same "proof" and exposes the children, although she has not been unfaithful.
- In L. M. Montgomery's A Tangled Web (1931), a woman never named the father of her illegitimate baby. When one couple separated the night of their wedding, some of the speculation was that he confessed to being the father.
- In the Temps story "The Oedipus Effect", when Dr. Sweetland is outlining his theory that a man was killed by subconscious telekinesis, part of his evidence that the alleged killer might want the man dead is that the victim's young son just happens to resemble the accused.
- From the start there is speculation as to whether the father of Isabelle's children is Charlie or her husband in The Thirteenth Tale.
- Robert A. Heinlein:
- Time Enough for Love, Lazarus Long time-travels to his own childhood, with a story about having been a foundling. The family resemblance, combined with the backstory Lazarus (going under the name "Ted Bronson" at that point) provides, leads his mother Maureen and her father Ira to conclude "Ted" is the illegitimate child of Ira's late brother. Later on, Maureen admits to Lazarus that her father thinks it a good deal more likely that "Ted" is Ira's own son.
- Lazarus also mentions that over his centuries of life, he's quite certain he raised children who were not his. He says that he was especially careful to be a loving father to such children.
- Later in the story, Lazarus is involved in a group marriage, where one of the rules sidesteps this: no matter how long you're involved, any babies born in the meantime means you stick around until they're grown. You may not be the father, or mother but you will raise the child.
- I Will Fear No Evil, when protagonist Johann tells a friend that none of his three putative children were his biological offspring (all were blood type O, Johann type AB). He loved his kids anyway.
- Time Enough for Love, Lazarus Long time-travels to his own childhood, with a story about having been a foundling. The family resemblance, combined with the backstory Lazarus (going under the name "Ted Bronson" at that point) provides, leads his mother Maureen and her father Ira to conclude "Ted" is the illegitimate child of Ira's late brother. Later on, Maureen admits to Lazarus that her father thinks it a good deal more likely that "Ted" is Ira's own son.
- Jacky invokes this trope in Under The Jolly Roger. She knows she's shortly to be deflowered by Captain Scrogg, so she decides to sleep with Robin. Her reasoning is that if she becomes pregnant, whoever the father is, she'll be able to tell herself it's Robin's baby and be able to love it the way it deserves. It doesn't work, but neither does Captain Scrogg's Attempted Rape, so it all works out.
- Barrayar in Lois McMaster Bujold's Vorkosigan Saga is only acquiring the tests in the middle of the saga. Early, Cordelia shocks her father-in-law by pointing out that paternity is uncertain; a major plot in A Civil Campaign revolves on the revelation of, several generations earlier, a count's heir actually being another man's child—a Cetagandan's child—and in Captain Vorpatril's Alliance, Ivan observes that testing is turning up more and more Cetagandan blood, people being only human. In the series' present, this trope is being eliminated now that most children are conceived and gestated via uterine replicators.
- Warrior Cats: Bluefur never revealed who sired her kits. Her Clanmates assume that Thrushpelt is the father of her kits. Mistykit and Stonekit have Bluefur's color, but Mosskit doesn't resemble either Thrushpelt or Bluefur. She doesn't resemble her biological father Oakheart either.
- Defied in Wax and Wayne. Steris's marriage contract with Wax stipulates that both of them can have affairs, but she won't have any illicit sex until they've produced an heir. Since Wax is the one who brought the noble title into the marriage, it's important that the heir is really his.
- The Wicked Years:
- Inverted in Wicked, in which Elphaba isn't sure if Liir is her son or not because she'd been unconscious at the time he was born and no one would tell her if she'd given birth during that time or not.
- Although Played Straight with her sister Nessarose, who her father suspects is not his. Turns out it's true about Elphaba, too, with a different father than her sister, though. The issue of both claims is resolved by sequel books, where Liir's daughter turns up green, confirming Liir's parentage at last and the family tree confirms that Nessarose is indeed Frexspar's child
- A non-human example in Harry Turtledove's Worldwar series. The Race have a mating season, during which their females start producing pheromones that drive males crazy. A male's mating display (raised crest) drives a female crazy, and they proceed to do it anywhere they happen to be at the moment. The concept of family does not exist, and hatchlings are raised (or, to put it better, domesticated) communally by females. Any other time of the year, they don't think about sex at all. The same is true by the other two races conquered by the Race: the Hallessi and the Rabotevs. They are disgusted when they learn that humans mate year-round and form permanent bonds. However, since ginger causes females to temporarily produce pheromones, some members of the Race have also started to have regular sex, and normal male-female friendships evolve into permanent bonds and raise their own hatchlings, although this practice is considered obscene by the majority. On the other hand, The Emperor has a harem of females kept away from any other male specifically for the purpose of having an unbroken dynastic line. This has worked for over 50,000 years.
- In the Maeve Binchy novel Minding Frankie, Noel's terminally ill girlfriend asks him to care for the baby she is about to have, which she says is his. He raises Frankie as a single father with the help of an almost literal village of friends and neighbors. Towards the end of the story, he decides to submit his DNA and Frankie's for comparison.It turns out that he is not Frankie's biological father, but he decides to keep on letting everyone assume that he is.
- The White Bone: Not only do the elephants not know who their fathers are, they don't even know that a bull's seed is required to create a calf. They believe that a bull digs a cow's calf tunnel, making her capable of giving birth, but she produces the calf by herself.
- In Mouse, there are two candidates for Mouse's father: a sorcerer known as Priest, and an embassy worker who left before Mouse was born. June thinks it was probably the embassy worker.
- An episode of Airwolf involved Stringfellow meeting the Vietnamese woman that his missing brother St. John had been having an affair with during the war. She has a son of the right age, but no one is sure if the boy really is String's nephew and Sinjin's son or not.
- Almost Family: Leon Bechley inflicted this on a hundred or more couples, as he used his sperm to perform IVF, not the men's. As a result, dozens of people come out to connect with each other/him or sue (he's also indicted for committing fraud and sexual abuse on a huge scale).
- In the Black Adder season 1 episode "Born to be King", Prince Edmund thinks he has letters that show the Queen had an affair with the Duke of Argyll nine months before his elder brother's birth, which makes Harry illegitimate and himself the heir to the throne. Unfortunately, he's being set up and hasn't checked the dates ... they're actually from nine months before he was born.
- Borgia: Lucrezia is sleeping with two men around the time her second son is conceived. Funnily enough, they're both named Alfonso. She is never sure which Alfonso fathered the boy.
- One episode of Brooklyn Nine-Nine has Jake and Terry questioning a suspect in a blackmail case, whose motive is that each of the two victims had slept with his wife. While the suspect turned out to be innocent (and had in fact been completely unaware of his wife's infidelity), after extricating themselves from the situation Jake and Terry uncomfortably note that the couple's young son looked very similar to one of the victims.
- Allowed to play for nearly two seasons in the case of Rebecca on Brothers & Sisters. Initially, she is presented as William Walker's illegitimate daughter by his long-time mistress Holly Harper. Although the issue of getting a Daddy DNA Test was raised, especially by lawyer brother Kevin, this was largely treated as unreasonable and the family accepted her as William's daughter. Until Rebecca and her supposed half-brother Justin began having romantic feelings, at which point she got tested and it was confirmed that she was actually the daughter of Holly's other boyfriend David.
- On Chicago P.D., Lindsey finally meets her father and they start bonding but a DNA test reveals that they are not actually related. The man is so angry at the reveal that he accuses Lindsey and her mother Bunny of running a con on him. Bunny defends herself by saying that she really thought the man was Lindsey's father. Bunny is The Alcoholic so her recollection of the events cannot be really trusted.
- Dickinson: Austin states he's unsure whether Sue's baby was sired by him or not, due to her affair.
- The Doctor Who episode "A Good Man Goes to War" plays with this trope, repeatedly and rather clumsily attempting to cast doubt on the paternity of Amy's baby. The answer: it IS her husband Rory's, but because the baby was conceived in the TARDIS, she is also a Time Lord.
- Farscape: During the Peacekeeper Wars miniseries Commandant Grayza is heavily pregnant. As Peacekeeper women are genetically modified to hold a pregnancy in stasis for up to seven years it's unclear who the father of her baby actually is. Her superior officer, Chancellor Maryk, acts as if it's his but the timing means it's possible that the child is actually John Crichton's. The show never confirms who the father was.
- Subverted in The Fresh Prince of Bel-Air. On "Mama's Baby, Carlton's Maybe", Carlton's ex-girlfriend Cindy comes back into his life with a baby. Carlton adamantly claims the child is his while his parents desperately try to persuade him to get a paternity test to prove he's not, so he won't have to raise a family so soon in life, but it turns out he knew all along the child wasn't his because he never had sex with anyone. It seems he just couldn't bear the thought of her having slept with someone other than him since he'd never truly let her go, nor could he entertain the idea of exonerating himself by admitting he was a virgin. For her part, Cindy only sought him out after having her baby because her parents kicked her out for doing so; they only intervene and take her back when she tells them she's going to marry Carlton at a rapid-service chapel.
- Game of Thrones plays it both straight and inverted: in season 1 it's revealed that Joffrey isn't actually Robert Baratheon's son, but rather Jaimie Lannister's by Twincest, and then in season 7 it's revealed that Ned Stark isn't the father of Jon Snow, but rather that his mother was Ned's sister Lyanna by Rhaegar Targaryen; therefore Mama knows who the father is, but Jon doesn't know who either of his true parents are. It should be noted in this last instance, Ned Stark did know who Jon's real parents were: but chose not to reveal this information to protect Jon from his friend Robert Baratheon.
- The Get Down: Towards the end of the series it's confirmed, after a lot of hint-dropping beforehand, that Mylene Cruz's "uncle" Francisco is actually her biological father, making her "father" actually her uncle. Her mother, Lydia, was in love with Francisco in their youth but settled for Ramón who was a budding pastor and seemed more stable. Even before the reveal Mylene is a lot closer to Francisco, who is willing to do anything to help build her music career, than Ramón who is a typical Fantasy-Forbidding Father who violently opposes her interest in disco.
- In The Goodies future episode "2001 And A Bit", the Goodies have all had sex with the same woman who then gave birth to triplets. So each Goodie picked one as his son — turns out they all picked the wrong ones. Therefore Graham Jr is a violent working-class yobbo like Bill Oddie, Bill Jr is a toff like Tim Brooke-Taylor, and Tim Jr is a scientist like Graham Garden.
- An episode plays with and lamp-shades the gender double-standard of the trope when the title character tries to do a Daddy DNA Test on Taub's kids (from simultaneous pregnancies with the two woman he had been seeing). After a moment of weakness, Taub shreds the results without looking.
- Gregory House himself suspected that his legal father, a strict military man, wasn't his biological dad, telling him as much out of spite for the corporal punishments that were meted out to him during his childhood. A DNA test conducted after his father's death confirmed this. However, the family friend whom House suspected to have fathered him (and did have an affair with his mother) turns out to be genetically unrelated as well. He never considers testing his mother.
- In an episode of In the Heat of the Night, a man finally snaps and murders his wife and her lover after catching them together in their bed. The investigation reveals that the affair has been going on for years and that it's highly likely that he's not his son's biological father — he refers to his daughter as "the only child I can truthfully call mine!", even though it's implied he had doubts about her paternity as well.
- In The L.A. Complex, Raquel gets pregnant by either Connor or Gary (it's left ambiguous.) Before she finds out who the father is (or reveals it to the audience), she miscarries.
- In an episode of Law & Order: SVU, a man discovers that the child he's been raising isn't really his. His wife turns out to have a boyfriend, claiming that her husband is a workaholic, and doesn't feel ashamed about lying about her child's paternity. When the couple starts divorce proceedings, the husband discovers that he's stuck paying child support for a baby that isn't his, as the law doesn't care about the child's biological father, unless that man marries the mother (Truth in Television, in many cases, the judge will rule in favor of the child, even though it may look like he or she is ruling against the wronged party; some judges will make a note of that, though).
- While they're working that case, Stabler becomes very aware of the fact that he and his wife have been estranged for a long period of time and that she'd become pregnant around the time of their reunion, meaning he could very well be in the same exact position. His wife is offended when he hints at the possibility; she later sincerely assures him that he is the biological father of all their children, and he doesn't feel the need to confirm it.
- Lost Love in Times: Yuan Ling is actually the son of Yuan An's older brother. His mother, Consort Lian, lied about his paternity. (With some help from Tao Yao and Xi Xie, who magically delayed the baby's birth.) Yuan An only learns the truth when Yuan Ling is an adult. Yuan Ling himself doesn't find out for another two years. The resulting drama is... ugly.
- Lovecraft Country: It turns out that Atticus might be George's son biologically, since he had an affair with his mother. His father admits he's not sure. Since this is the 1950s, there's no medical means to resolve it.
- In the Malcolm in the Middle episode where Betty White guest stars as Sylvia, the secret wife of Victor, Lois' father, has Lois trying to talk her into allowing Ida, her mother, to have Victor's tiny pension, since the lawsuit Ida was preparing to launch would destroy her financially even if she won. Sylvia refuses on the grounds that she hates Ida so much, so Lois decides to fully support Ida's lawsuit. As they are preparing the court documentation, they receive the DNA test the lawyer advised Lois to take, and she's shocked to discover that she is not related to Victor at all. Ida nonchalantly admits that Lois' biological father is a guy from the old country who could walk upstairs on his hands, and even admits that Susan, Lois' sister, may have been fathered by another man.
- Happens practically Once an Episode on Maury. "You are/are not the father!" is a preferred Catchphrase of the titular host, who invites couples on his show to do DNA tests to see if the man in question is the father of a child or not. It gets to the point where women have had to come back several times to try and find out, including one woman who tested 17 men without success.note
- Mosley. Oswald Mosley is having an affair with the wife of an MP. When she informs him she's pregnant, Mosley advises her to seduce her husband double-quick. "There's many men who are happily father to children who are not their own." Unfortunately, she points out her husband is out of the country.
- On The Musketeers, Aramis has an affair with Queen Anne who she reveals she's pregnant shortly afterwards (after years of unsuccessful trying with the King). Aramis immediately knows it's his child, although Athos reminds him that he can never claim the child because that will result in his and the Queen's death.
- On My Name Is Earl, this comes up more than once. The first time is when Joy is pregnant (for the second time, having been visibly pregnant already the night she met and married Earl), and Earl thinks the baby is his... but she has been sleeping with Darnell, and the truth comes out 9 months later. It comes up again with her first child, Dodge. In what turned out to be the final episode, Earl learns that Joy has never told Dodge that Earl is not his biological father, prompting Earl to seek him out on Dodge's behalf. After discovering a likely candidate (a man whose wealth and connections could improve Dodge's life if they were to develop a relationship), Earl has Dodge's DNA tested and finds out that he himself is Dodge's biological father. He just didn't remember Joy, whom he had casual sex with at a costume party when she assumed he was the other man. Earl also finds out that Earl Jr. isn't really Darnell's, as was previously thought.
- In Still Open All Hours, Leroy's mother, pregnant after a one night stand, dumped the baby on Granville. The fact she was the sort of woman to do this leads Leroy to wonder if Granville is really his father, but everyone else in the street sees the resemblance.
- On Poldark, Elizabeth gives birth to a child that could either be her husband George's or the result of her night with Ross.
- Red Dwarf: In "Dear Dave", Lister receives a letter from an ex-girlfriend telling him that she's pregnant and she's not sure if it's his child or that of a man she works with. Since the letter arrived several million years late it's a moot issue but Lister wants to know if it was his anyway. At the end of the episode he finally finds her next letter and after reading it angrily denounces her as a "slag", indicating that it turned out her baby wasn't his.
- Antonia's paternity is unknown. Agrippa asks Octavia whether he or Antony is the biological father, though how he expected her to be able to answer that isn't expounded on. Toddler Antonia's very brief appearances give no clues. She's blonde, which could imply Agrippa is the father; however, her maternal uncle, Octavian, is also blond, and many white children do have blond/e hair that becomes much darker over the years. Historically, Antonia's paternity was never debated.
- Cleopatra takes advantage of this trope. Wanting to have a child with Julius Caesar, but not having met him yet at a time when she's biologically most likely to have a child, she seduces a lusty Roman soldier.
- Lucius Vorenus finds out that his daughter's supposed child is actually his wife Niobe's, causing her to commit suicide.
- An episode of Sanford and Son has an old friend of Fred's claim that he had a one night stand with Elizabeth and that he's actually Lamont's father. Another friend of Fred's actually says the trope name verbatim. At the end it turns out that the guy actually slept with Aunt Esther, and thought it was Elizabeth in the dark.
- Alex in Saving Hope gets pregnant after sleeping with Charlie and Joel. She chooses to wait until after the baby is born to do a paternity test due to potential danger to the fetus if they tried to test in utero. In the season finale, while Alex is giving birth, Joel dies. Alex and Charlie then rekindle their relationship and raise the baby together, waiting almost a year to resolve the looming paternity issue. By that point, Charlie decides that he will keep loving their son regardless of genetics and they never get the test.
- Still a viable trope on Shameless (US). Mickey Milkovich was forced by his father Terry to have sex with a prostitute named Svetlana in order to "fuck the queer" out of him. It didn't work and Svetlana became pregnant. However, because of her job, it is not clear that Mickey is actually the father. But being dirt poor, a DNA test is not as readily available an option as it would be for more affluent characters. Also, Svetlana has not given up on "curing" Mickey, since she was able to use the pregnancy to force him to marry her with the full support of Terry and she probably would not cooperate with any attempt to disprove Mickey's paternity.
- Tim and Corrine get married, and Corrine quickly becomes pregnant. She's 5 months pregnant when they've only been married for 3 weeks. She assures Tim that she hadn't had sex with anyone during that time before they got married but Tim doesn't believe it. A week or two later she has the baby and it's possessed, which is why it grew so fast.
- Burt gets Abducted By Aliens and replaced with an alien double. After that plot is resolved, his wife Mary learns she's pregnant. At first, she's thrilled, but then realizes that the baby could be Alien!Burt's rather than Human!Burt's.
- Spartacus: Blood and Sand: It would be hard to say who got Lucretia pregnant, although she thinks it was Crixus. Given that she's been trying to have children with Batiatus for years with no success, this may be right and he's infertile. We never learn with certainty though. If she'd given birth, it might have been clear (as the child, if Crixus', might have dark skin too), but that doesn't happen.
- In season 9 of Stargate SG-1, Vala, while trapped in the Ori galaxy, gets married to cover up the fact that she got pregnant out of wedlock. The truth does eventually come out, though: the Ori impregnated Vala with the Orici, who is basically the in-universe version of the Antichrist. Vala's husband initially thinks the child is his until one of the Priors (basically, the Ori's prophets) tells him that he's sterile. He then thinks Vala cheated on him for a short time before it's officially revealed that the child is "the will of the Ori."
- Terriers: Britt's girlfriend Katie gets pregnant shortly after having sex with her professor, which makes her afraid to tell Britt about the pregnancy because she's not sure which of them is the father. Britt is initially angry, but eventually tells her he doesn't want to know the result of the paternity test because he wants to believe the child is his.
- In Trailer Park Boys, Trinity is by all accounts Ricky's daughter, but the series has dropped the odd hint that she might actually be Julian's daughter, as evidenced by the fact her personality far more resembles his than Ricky's. It doesn't help that her mother Lucy has been around the park a few times... No official word on whose daughter she really is has ever been confirmed.
- True Detective: Velcoro and his wife were trying to have a baby when she was raped. Almost exactly nine months later, she gave birth to a red-headed child who looks nothing like Velcoro. The couple chooses to treat the child as Velcoro's son. When they separate, however, the wife threatens to do a DNA test, which could remove all of Velcoro's custody rights if their son isn't his biological offspring.
- On Two and a Half Men, Alan's ex-wife Judith has a daughter with her current husband Herb. Alan, however, suspects he might actually be the father since he and Judith had a brief affair while she and Herb were separated (not to mention the baby resembles Alan a great deal).
- Also, while it is played for laughs, near the end of one episode we see multiple men who were regularly at Judith's house for professional reasons (such as a Postman) who all greatly resembled Jake.
- A major plot point in the first season of Veronica Mars. Hinted at a little, then kicked into high gear with the bombshell "I told him I'd get a paternity test and take him for millions."
- On The Walking Dead, when Lori gets pregnant, Shane thinks he's the father instead of Rick. Lori shuts him down, and he dies before Judith is born, so it hasn't really come up since; even the few people left who knew Shane don't question that Judith's Rick's daughter. In season 7, Rick says that he thinks that Judith is Shane's daughter but it does not change how he feels about her.
- Daryl jokes (out of Rick's earshot)that Judith is Shane's; the reactions of the others show they at least entertain the possibility.
- The White Queen: King Edward IV may be illegitimate if he was born from his mother Duchess Cecily's affair with an archer instead of her husband Richard of York.
Cecily: Unless I should unseat [Edward IV].
Jacquetta: And how would you do that, Duchess Cecily?
Cecily: I could disown him. I could put his brother George upon the throne in his place.
Jacquetta: Yes, I did hear some talk when Edward was born. Um, it was an archer, wasn't it? By the name of, um Blaybourne. That's it, yes. People said that you had made a cuckold of your husband, but in fact, I was of the few who swore that a lady of your standing would never stoop so low, and yet it seems you did. If that is what you're saying, Duchess Cecily, that you admit yourself a common whore and declare your son, the king, a bastard? For I cannot see how else you would unseat him.
Cecily: Enough! Enough.
- Edward himself isn't certain of his paternity:
Elizabeth: Why would [Cecily] back George instead of you?
Edward: The old story. Whether I am my father's son, whether I am legitimate! George is saying that I am a bastard and that would make him the true York heir.
- Edward himself isn't certain of his paternity:
- In the folk song "Rocking the Cradle", the singer believes his wife has "left me with a baby who's none of my own".
- A traditional Trinidadian song, "Shame and Scandal", is basically a gender-flipped version of Johnny Be Fair (mentioned above).
- In Mitch Benn's "Lullaby For the Real World", amongst the truth bombs he drops on an unfortunate kid is "Your real dad is the man you've always known as Uncle Kevin".
- The Grateful Dead touch on this in "Friend of the Devil":
Got a wife in Chino, babe
And one in Cherokee
First one says she's got my child
But it don't look like me
- Invoked in the Kid Creole and the Coconuts song "Annie, I'm Not Your Daddy", sung from the point of view of a man telling his wife/girlfriend's daughter that he isn't her real father. The words "Mama's baby, Papa's maybe" are sung by a female backing group representing the titular Annie.
- One Jewish legend states that when Sarah finally got pregnant, gossip claimed that the father was not Abraham but Abimelech—after all, she had lived with Abraham for decades without conceiving and had been taken into Abimelech's house right before the pregnancy happened. God gave Isaac and Abraham a Strong Family Resemblance just to stop the rumors.
- Another has it that David was believed to be a product of adultery for most of his early life - after multiple children his father stopped having sex with his mother because of belated anxiety about whether his Moabite ancestry (from Ruth) meant he was forbidden to have relations with a Jewish woman, and his mother pulled a Bed Trick when he tried to sleep with a servant instead.
- And a third has it that David's son Chileab was changed in the womb to look more like him again because of divine intervention to keep his paternity from being questioned - his mother, Abigail, had been very recently widowed.
- In Classical Mythology, Zeus has a reputation for sleeping around. So when a woman, called Semele, finds herself pregnant by a guy who says he is Zeus (and he is), Hera (Zeus's wife and yandere extraordinaire) decides to visit the expecting woman in disguise. She tells Semele what boils down to "Oh dear, he can call himself anyone, get him to prove he is Zeus by appearing in his godly form!", and Semele decides she has a point. She convinces Zeus to do just that and gets burnt to a crisp, since humans cannot handle seeing Gods' true appearances, and after Zeus retrieves the immortal fetus he brings it to term in his thigh and thus Dionysus/Bacchus born. A later story, told in the play Bacchae, has people from Semele's city (including her own sisters) doubting Dionysus's parentage and thus (by that point hard-earned) divinity, which he... does not take well.
- Exalted: Plays into the differences in stigma between illegitimate children in the Scarlet Dynasty; a woman's child is definitely the child of a Dynast, meaning they have to be raised according to the usual (expensive) standards regardless of how their uncertain parentage makes their chance of Exalting less likely (as well as their unknown bloodline making them a poor marriage prospect), while male Dynasts can opt in or out of claiming their bastards (although there are still strong pressures to claim and financially support them from the outset). The concern there is less about who the parents are, and more about management of the Super Breeding Program.
- William Shakespeare
Prospero: Thy mother was a piece of virtue, and
- In The Winter's Tale, Leontes doubts that he is the father of either Mamillus or Perdita. (He's the father of both, but Improperly Paranoid.)
- In The Tempest, Prospero tweaks the edge of this trope, explaining the past to Miranda:
She said thou wast my daughter;
- In Titus Andronicus, he opts for the Chocolate Baby solution—the child is obviously Aaron's.
- In The Merchant of Venice, Lancelot argues that Jessica should hope not to be Shylock's daughter.
- In Much Ado About Nothing, Don Pedro asks Leonato if he is Hero's father and his response is "Her mother hath many times told me so." It's clearly meant to be a joke, though. (His wife may actually be standing right there as he says it, though she's a ghost character.) However, men's fear of being cuckolded is played rather seriously as a theme throughout the play.
- Also, right after this line, Benedick asks if Leonato was in doubt when he asked his wife, and Leonato responds with "Signior Benedick, no, for you were but a child then."
- The Bible: The Complete Word of God (abridged) makes something of a Running Gag about Mary and Joseph. At one point, they get a letter from Jesus which is addressed, "Dear Mother and Joseph."
- August Strindberg used this as a strong plot point in Fathers. The main character is slowly Driven to Madness because of his inner doubts concerning whether or not he is the actual father of his daughter.
- In Euripides's Ion, Apollo exploits the difficulty in telling: his oracle tells Xuthus that Ion is his son when in fact, he is the son of Xuthus's wife Creusa who was raped by Apollo before meeting Xuthus and abandoned her child in the woods. Xuthus and Creusa married but never had children, so Xuthus went to Apollo's oracle for help. The oracle told him that the priest outside talking to his wife was his son, and Xuthus himself wondered if this was his biological child by some other woman or a "gift" from Apollo. Only after he leaves does Athena appear, explaining that Ion is the child Creusa bore Apollo but who will now be considered Xuthus' instead.
- This trope is played straight in Mamma Mia!, despite the musical having been written after DNA testing became possible. One can speculate that it wasn't practical in the time frame before Sophie's wedding or wasn't available in the setting of a remote Greek island. In any case, DNA testing is never even suggested as a solution to the plot.
- Pokémon Live! has implications that Ash's biological father might be Delia's ex-boyfriend Giovanni of Team Rocket, not the man she's married to.
- In Strange Interlude, Nina's husband Sam has a history of insanity in his family. So Nina elects to get pregnant by her friend Ned and pass the baby off as Sam's.
- Crusader Kings II: The "Way of Life" DLC has the Seduction focus, which is exactly what it sounds like. There's also an event chain where your character thinks that he might not be the father of his pregnant wife's child, and can hire spies to try and catch her at adultery. Be prepared to have your character suspicious of every pregnancy if you have the Paranoid trait. This can also be Gender Flipped if you play as a female ruler: you can run around behind your king consort's back and sometimes fool him into thinking any "accidents" are his.
- Interestingly, if you suspect your wife and hire spies, both attempts to learn the truth may come back with a false negative that your wife was faithful. However, the child's "graphical culture" can help you identify a hidden bastard child. Graphical culture is inherited by a random parent. If you and your wife are both Irish, but her most recent child is light blond boy, it might be time to start looking at your German courtiers (Graphic Cultures typically are typically shared among a cultural group, but all cultures have a much more limited pool of childhood portraits than adult portraits, creating a very easy expectation of what your child should look like given his married parental cultures.).
- Stardew Valley: It's really heavily implied that Abigail is really the daughter of the Wizard who lives at the edge of town and not Pierre. Think about it: Pierre has very little common with her, the Wizard has a lot in common with her (and suspects he has an illegitimate daughter somewhere), and Caroline used to wander the area where the Wizard lives until Pierre stopped her from going there.
- Also comes up in the unofficial expansion mod Stardew Valley Expanded if you have mature events enabled. A questline here outright confirms that Abigail is the Wizard's biological daughter, conceived during a period when Pierre and Caroline were having relationship problems. The timing was such that Caroline was never sure who Abigail's father was, until Abigail starts displaying some of the Wizard's abilities and affinities with magic.
- In one path of School Days, Sekai turns up pregnant and insists that Makoto is the father. The player gets the choice on how to react to this, but unusually for this series, Makoto is perfectly justified in reacting badly, because the timing of the situation makes it very likely that Sekai's baby was actually fathered by Taisuke; he ends up telling Sekai that he'll only get back together with her if she has an abortion. Less unusually for this series, Sekai will respond by either murdering Makoto or murdering Kotonoha, depending on whether or not you brought up your suspicions about Taisuke being the father.
- The shapeshifting Abel from Dan and Mab's Furry Adventures endured rumors of illegitimacy while growing up. While he greatly resembled his mother May, he didn't much look like his father Cid. The fact that he was born with wings combined with his mother's reputation as a "loose" woman led to the neighbors talking. Many years later, the truth comes out: His mother was entirely faithful, but his father was actually a Cubi shapeshifter named Aniz who killed the real Cid and has been impersonating him all these years. Abel's resemblance to only his mother is the result of Cubi's tendencies to take after their non-Cubi parents.
- In Doc Rat, Cedrci refused to believe that he was the father of Dani's babies.
- Girl Genius: Played with. The first child of Bill Heterodyne and Lucrezia was named Klaus Barry Heterodyne, after Lucrezia's old boyfriend Klaus Wulfenbach and Bill's brother Barry. The old seneschal stresses that the name was Bill's idea, and he was born over two years after Klaus Wulfenbach disappeared.
Carson: You'd be shocked at how many people just ignore the math!
- Keychain of Creation brings it up during a dispute between Marena and her abusive politician mother:
Marena: You're not my mother, Aria!!beatAria: No... I was in a position to be certain, petal. Now if you were unsure of your fa—
- Scandinavia and the World has Grandpa North delighted that he discovered after his year-long sea trip that his wife is pregnant. When Sweden points out the obvious — that there's no way he could be the biological father because he was at sea — North brushes it off, saying that since it's his wife that's pregnant, legally speaking he gets to claim the child as his. He even called the biological father an idiot for impregnating someone other than his wife, since now he misses out on raising this child.
- Averted in TwoKinds; even though every other character is suspicious of the actual parentage of Flora's child, since it's "Common Knowledge" that humans and keidrans cannot interbreed, Trace himself, the purported father, has absolutely no doubts as to Flora's loyalty to him and the child's subsequent parentage. Even when Flora herself is filled with doubts as to how Trace is actually feeling, Trace himself is shown calmly planning a list of baby names.note
- Noob: La Quête Légendaire has the inverse be the case for Sparadrap and his younger brother. An established female character turns out to be an ex of his father who had a son with him, but his father can't remember whose mother she is by virtue of being a Forgetful Jones and the potential mother can't thanks to a Lobotomy. And in the process of trying to remember, the father reveals the existence of a third son of his to the audience.
- In American Dad!, when excessive partying with an old friend of her mother's causes one of Hayley's kidneys to die and the other to begin failing, necessitating a transplant, Francine is forced to reveal to Stan that he may not be Hayley's father. Three days before their marriage and subsequent consummation, Francine cheated on him in a moment of cold-feet-fueled weakness at her bachelorette party largely caused and galvanized by the same hard-partying girlfriend who wrecks her daughter's kidneys twenty-some-odd years later. Unsure of Hayley's actual paternity, Stan demands a test while Francine insists on finding the other man just in case Stan isn't a match for Hayley's transplant, and along this adventure, Stan struggles with the idea that he's raised Hayley and devoted so much time and love to her and yet may not be her father. Eventually, Stan comes to realize that regardless of her paternity, Hayley is still his daughter, and when the results of her paternity test are presented to him he declines to read them.
- On multiple occasions throughout the episode, when asked by Francine if he can forgive her infidelity, Stan holds her tenderly in contemplative silence before calling her a slut and then remarking off-handedly in bewilderment on his body language, and the mixed signals it must be giving her.
- The titular protagonist has at least three potential fathers, including the heads of the KGB and a rival spy agency. Much is made of his mother's promiscuity, which hasn't slowed down in the slightest.
- In another episode, Archer gets sued for paternity but is so desperate to get out of it that he switches another man's blood with the sample they took from him (through an elaborate Mission: Impossible scenario). He is then confirmed as the father and must pay child support — only then realizing he is not the father and put the real father's blood in his place.
- Brought up in Avatar: The Last Airbender The Search but ultimately averted — with the timing between the wedding and Zuko's birth Ozai knows his son is his. Ursa only claimed otherwise because she wanted to see if her husband was intercepting her letters, and hurt him if he was; she is powerless and cut off from her friends and family and can only wish that Zuko is nothing like Ozai. Knowing this, Ozai decides to be far crueler to Zuko out of spite.
- Zig-zagged on BoJack Horseman. Hollyhock suspects that Bojack is her father because she looks like him, and a DNA test proves they're a match. However, he has no idea who her mother is since he Really Gets Around (and in a World of Funny Animals, her mother could be human or any type of animal). They find a list of all his girlfriends/one-night-stands made by a Loony Fan and go through the list, but none of them are her mother. Later in the season, it's revealed that she's actually Bojack's sister, through them sharing a father, and her mother was his parents' maid.
- The titular Kevin Spencer could be the child of his father Percy, or Percy's brother Lester. The boy's mother, Anastasia, flipped a coin on the prospect and Percy "won". Percy, who is all too happy to escape his family, eagerly wants Kevin to get tested... But Kevin, preferring his life with Percy over a potential life with Lester, threatens Percy and the issue is dropped entirely.
- In King of the Hill everybody knows that Dale's son, Joseph, is really John Redcorn's child — everyone except Dale and Joseph (and Peggy for an embarrassingly long time), that is.
- Eventually John Redcorn wants to reveal the truth to Joseph, but Nancy (the boy's mother) refuses to allow it based on the strong bond Joseph and Dale share. As she puts it "Joseph already has the only father he'll ever need".
- Indeed, Dale and Joseph even discover that Dale was out of town the night Joseph must have been conceived but convince themselves that she was simply abducted by aliens and impregnated with her husband's genetic seed (for some reason) that night.
- Another episode involved a former lover of John Redcorn's (a single mother with a darker-skinned daughter about Joseph's age) moving into the neighborhood and beginning to date resident loser, Bill. While Joseph and the daughter develop crushes on each other, Dale discovers via covert DNA testing that they are half-siblings. After convincing himself this means he is the father (via alien abduction and impregnation once again), he reveals the test and results to his wife, who confronts John Redcorn over this infidelity during their affair. Fortunately, Redcorn ends up taking some responsibility and the mother and daughter end up moving in with him, separating the girl and Joseph (without alerting them to their blood relation) before anything actually incestuous occurs.
- Eventually John Redcorn wants to reveal the truth to Joseph, but Nancy (the boy's mother) refuses to allow it based on the strong bond Joseph and Dale share. As she puts it "Joseph already has the only father he'll ever need".
- Moral Orel: One of the many strains in the Awful Wedded Life of Clay and Bloberta, Orel's parents, is that their youngest child, Shapey, looks nothing like Clay (he has blond hair while the rest of the family are brunettes), causing Clay to accuse Bloberta of an affair. It's revealed later on that Shapey is the result of an affair between Bloberta and Coach Stopframe, who ironically only impregnated Bloberta in order to get closer to his actual crush, Clay. "The Best Christmas Ever" has the two argue about it directly in response to their pastor's sermon about abortion earlier that day.
Bloberta: You know the reverend was referring to you not wanting Shapey!Clay: That's ridiculous! How would he even know?Bloberta: Don't be an idiot! Everyone knows you didn't want him.Clay: Yeah, well, I had my reasons. I think it's kind of strange that I don't even remember conceiving this kid!Clay: All I do is try to forget. At least you know he's yours.
- Hinted at in My Little Pony: Friendship Is Magic, of all shows. Mr. and Mrs. Cake are earth ponies but their kids are a pegasus and a unicorn, and Mr. Cake attempts to Hand Wave this to Pinkie Pie with an explanation that makes no sense involving the idea that traits can be inherited through marriage!
- In The Science of Adultery, Chapter 4 of his book The Third Chimpanzee, Jared Diamond describes a study conducted on newborn babies and their parents in the obstetrics ward of a hospital that was conducted in the 1940s by a distinguished medical researcher, who disclosed the result to Diamond only decades after the fact and still wished to remain anonymous. Dr. X, as Diamond calls him, was studying the genetics of human blood groups, which are molecules in the blood that people acquire from either their mother or their father. Dr. X merely intended to study how parents passed down these molecules to their children, but accidentally discovered that nearly ten percent of the babies in the study were the fruit of adultery! This is because some of the babies had substances that were not in the blood of either of their ostensible parents and since the samples were taken soon after the baby emerged from its mother, the only explanation was that the father was someone other than the mother's husband. Dr. X withheld the results of his study because such discussion of adultery would have been too explosive in that conservative time, but Diamond writes that later studies in the 1990s using DNA testing variously showed that 5 to 30 percent of American and British babies were adulterously conceived. These results have been challenged more recently by Maarten H.D. Larmuseau, a geneticist at the University of Leuven in Belgium, who points out that those DNA studies were biased by focusing on people who had reason to doubt their paternity. By using vast genealogy records and sequencing the Y chromosomes of men in a 2013 study, his team got results for various countries that were less than one percent, leading him to declare that widespread cuckoldry is an urban myth.
- It should be noted that Dr. X was testing babies conceived in Britain during the worst years of World War II. It's not surprising to find adultery more common in a time when the phrase 'eat, drink, and be merry, for tomorrow you may die' had real meaning.
- The use of DNA testing. In about three-quarters of the cases, the purported father finds he is the real father —which means, of course, that in a quarter, he finds he's not. Influencing these statistics is the fact that generally, a paternity test will only be performed in cases where there is both doubt about parentage and access to testing.
- On the Talk Show Maury, one person quoted the trope name. The guest who said it was a woman named Rachel, the mother of her two sons who were getting tested to prove whether or not they fathered their wives' children (and if so, making them her grandchildren); she was a real skeptic about the paternity and wanted confirmation from her friend "D.N.A." (It was the first of her two appearances on the show, and you can see/hear her say the trope name in this clip here on YouTube, not once but twice.)
- In Conn Iggulden's epic stories of the Mongol Empire, a recurring plot-theme concerns Genghis Khan's uncertainty over the paternity of his eldest son Jechi (at the time of conception, his mother Borte was a prisoner of the Tartars and was known to have been raped). Because he half-believes in the "this is a Tartar's bastard" stories, Genghis repeatedly shuns and blanks his oldest son, or else gives him punitive or seemingly impossible tasks to complete that he would not dream of imposing on the favoured younger sons. This had consequences that stretched down the generations and caused the Mongol empire to collapse prematurely.
- The whole reason Queen Isabella the I of Castille took the throne of her dead brother Enrique instead of his daughter Juana is due to the uncertainty of Juana's parentage; Enrique was rumoured to be "more interested in his guards than his queen" and the queen had many lovers and even several illegitimate children.
- Isabella's own parentage was seriously contested throughout her childhood, for exactly the same reasons: Juan II of Castille was even more openly gay than his son Enrique. Eventually, though, Isabella grew up to be her father's speaking likeness, which put doubts to rest.
- At the Oneida colony, the practice of "complex marriage" caused onlookers to wonder about the children knowing their fathers. The leader retorted that the children knew their fathers the way children outside the colony did: on the word of their mothers.
- Victorian anthropologists hypothesized that matrilineal systems were more primitive than patrilineal systems, stemming from before the organization of marriage so that only a child's mother could be known. This has not been borne out by subsequent research—but not before it had been imported in many historical novels, and Two-Fisted Tales.
- The practice in Egypt of the Pharaoh marrying his own sister was taken to be evidence of the Victorian theory, but since the Pharaoh's heir would be his own son even if he was not born to the sister, it appears to be a matter of regarding only his own sister as his social equal and so an appropriate wife.
- Also a matter of getting the strongest royal blood possible for the offspring—the stronger an heir's claim, the less likely a coup becomes, so getting it from both sides helps.
- This factored into the inheritance snarl around Hatshepsut and the Thutmoses. (Thutmose III was her nephew, and her husband's son, but not her child; her only offspring was a daughter. Thutmose II was her sickly half-brother, to whom she was queen, and who left her regent to his heir when he died young. Thutmose III's reasons for attempting to write her out of history have lately been suspected to be as much about downplaying the fact that he was only royalty on his father's side for his son's benefit as about resentment for the semi-usurpation thing, considering his timing.)
- Researchers in evolutionary psychology have noted that when a young child's resemblance to its parents is brought up in a family setting, it will nearly always be the mother's relatives commenting on the child's resemblance to the father.
- In some cultures, men may act more paternal to their sister's son than to their (alleged) own, as they can be sure they're related to the nephew in question. In many Native American chiefdoms, the heir to the chief, if it be a culture that was hereditary, was his maternal nephew through his eldest sister.
- Roman law neatly averted this trope, at least in theory; "the father is he to whom marriage points." In other words, legally speaking, biological parentage was irrelevant; the mother's husband was responsible for the child, period. This led to strict enforcement of "My Girl Is Not a Slut"-style customs, and it was not unknown for a father with a questionable child to exercise his right to kill the infant.
- Even today, there is a (rebuttable, meaning it can be disproven with DNA testing) legal presumption that the husband of a woman is the father of any child she has. The "psychological parent" doctrine also states that after a child bonds with the man they believe is their biological father, if it turns out to not be the case this man will still be treated legally as their father and have the obligation to pay support, for the child's mental health. Of course, if the man is proven not to be their biological father that may put a crimp in their relationship after that point anyway.
- This continues: one of the few cases in which Justice Antonin Scalia has written the opinion of the court is Michael H. v. Gerald D. (1989), which holds that for the purposes of family rights under the Due Process Clause of the Fourteenth Amendment to the Constitution, the "tradition" of recognizing the mother's husband as the legal father of a child trumps any biological arguments unless the state in question has statutory provisions to the contrary. (The case involved a girl proven to be the biological child of the plaintiff; he petitioned for visitation rights, arguing that as the biological father he had a constitutional right to see his daughter, but as California did not at the time provide for visitation rights for the biological father of a child born to a woman married to someone else and who had never been married to him, his petition was denied.) This particular opinion caused a stir in the legal community, and Scalia, although joined in the holding by a majority of justices, was only joined in the whole opinion by Chief Justice Rehnquist.
- One less fortunate case: a woman still married to a man who had been in prison three years got pregnant and wanted to divorce him and marry her boyfriend before the baby was born, but an old law prevented divorce while a woman was pregnant, under the assumption that the baby *had* to be her husband's. That it obviously was not in this case was irrelevant; the baby would still be recognized as his.
- In the 6th book of his Histories (chapters 62-70) Herodotus tells of the problems faced by Demaratos, king of Sparta. When he got the news of his birth, the father, King Ariston, at first suspected that he had been fathered by the mother's first husband because Demaratos was born before ten months had passed since the wedding (for the Greeks, pregnancy lasted ten months) and he had had no children from his first two wives. So he rashly said "this cannot be my son" in the presence of some Ephors. Later he decided that Demaratos was his son after all and after his death, Demaratos succeeded to the throne. However, he got into an intense rivalry with the other king of Sparta, Cleomenes, who then accused Demaratos of not being Ariston's son, used Ariston's rash words as evidence, and called for him to be deposed. Since there was no DNA test then, the Spartans decided to consult the oracle of Delphi, which confirmed Cleomenes' accusation. So Demaratos was no longer king. However it later emerged that Cleomenes had bribed the priestess of Apollo (who was subsequently stripped of her office), and Herodotus notes that Cleomenes himself came to a bad end because of this blasphemy. In some desperation, Demaratos asked his mother if he really was Ariston's son or not. Her answer: in the third night after the wedding, a man came to her who looked just like Ariston, who slept with her, left wreaths with her and left. And then Ariston came and was surprised to see her wearing the wreaths. So it must have been a god who had taken Ariston's shape. (The wreaths turned out to have come from the temple of the heros (demigod) Astrabakos). So Demaratos' father was either Ariston or a god.
- Inverted by DNA testing in one case, where a woman was seeking benefits for her children. DNA could prove her boyfriend was the father but indicated that another woman was the mother — something that made no sense to the woman nor her doctors. She was actually charged with benefits fraud for supposedly claiming benefits on children who weren't hers, and was only cleared when she was directly observed giving birth to a child whose DNA test showed the same discrepancy. Eventually, it was discovered she was a chimera — her reproductive organs had different DNA than the rest of her.
- This trope is one reason why, in some times and places in history, it was considered perfectly acceptable for a man to be unfaithful on his wife and have mistresses, but if a woman cheated on her husband, she was evil, vile, wicked, a demon, a witch, a whore, etc, etc and could face serious punishment.
- During the Wars of the Roses, accusations of illegitimacy were often invoked by many factions to claim the throne.
- Warwick the Kingmaker was a serial offender. He pulled this trick once with Margaret d'Anjou saying that Henry VI was illegitimate (which might have been true). When he and Edward IV fell out, he came up with Plan B, saying that Edward IV's mother Cecily Neville (his aunt!) committed adultery and that the King was an illegitimate child of an affair with an archer called Blaybourne. Later, George Clarence (Cecily's third son!) stated that while Edward IV his elder brother was illegitimate, he was totally legitimate.
- Averted with Richard III. He never denied that the Princes were the King's children but used a document and legal precedent to point out that the King's marriage to the Woodvilles was invalid because of a prior engagement on the part of the King. Back then, an engagement was good as a marriage, and invalidated future marriages, thus leaving both Princes illegitimate.
- To add the complication further, the discovery of Richard III's remains and the DNA test of his body revealed there is a false paternity somewhere in the royal lineage. The scientists used the living descendants from the royal family (from the Somerset and Richard's sister in particular) matched Richard III's maternal DNA, but not the paternal. But where the false paternity occurred still remains unknown.
- Some female mammals, such as lions, chimpanzees, and rats, tend to mate promiscuously within their social group, many more times and with many more partners than is necessary for conception. This may be a countermeasure to prevent infanticide by the males of the same group, as a male which has mated with any particular mother can't be sure her offspring aren't his.
- One of the many tragedies of American slavery in the antebellum era was that slave lineages were traced through the mothers' bloodline only—because that's how livestock pedigrees are recorded.
- Some evolutionary psychologists theorize that this is one reason why women bond easily with young infants while men have an easier time bonding after a year or two... when the child has matured enough that family resemblances become obvious and the man is better-assured that it is biologically his.
- When Grover Cleveland was first running for President, his opponents discovered that he was paying child support to Maria Crofts Halpin, who had had a son out of wedlock. However, Halpin had been involved with several other men at the time, and it was unclear whether Cleveland was actually the father. He paid child support only because among them Cleveland was the only one unmarried.
- There's an old saying that goes, "You can't always be sure who your father is. You at least know who your mother is."note In Spanish, there's a similarly-themed saying that goes "Los hijos de mis hijas, nietos míos son; los de mis hijos, no sé si son", which translates to something like "My daughters' children are my grandchildren; those of my sons', I can't be sure."
- There is also a slightly misogynist old saying: "The reason that mothers are fonder of children than fathers is because they are more certain that they are theirs."
- In The Origin of the Family, Private Property, and the State, Friedrich Engels claimed this trope was the root of misogyny and the rise of the patriarch, as a mechanism to secure the inheritance of property. He based this primarily on the work of Lewis H. Morgan, whose anthropological evidence suggested the earliest human societies were communal matrilineal clans. Since he was the second-in-command of Karl Marx, his ideas and those of Morgan's by proxy were closely associated with communism and effectively dismissed throughout the twentieth century, although recent evidence has shown that there may actually be truth to early matrilineal clan structure after all.
- Norway has a tradition for writing books on local history, telling of specific farms and the families connected to them. In one particular case, the authors were very thorough on everybody who ever was registered as living in their home area, but this area went batshit when the same authors insisted on using the term "written father"—that is, the father registered in the clerical records. In some cases, the "written father" was, of course, not the real one, and the term cast doubts over a lot of people and their heritage.
- It was rumored for years that the youngest child of Franz Josef I of Austria-Hungary and his wife Elisabeth/Sisi, Marie Valerie, wasn't actually Franz's daughter but the child of Sisi's close friend and admirer Gyula Andrássy, the Hungarian Prime Minister. Since Valerie grew up to be very physically similar to Franz, the rumors went away with time; Valerie herself, however, was traumatized by them and ended up disliking anything Hungarian.
- Britain's Prince Harry has been subjected to speculation about this since he was born—reportedly, his father's first words upon seeing him was shock and disappointment at his red hair, thanks to his coloring being more like that of one of his mother's lovers rather than his father's, despite insistence from all parties that their affair didn't begin until several years after his birth and that red hair is a trait from his mother's side of the family.
- In 1970, scandal erupted in Hollywood after Patty Duke revealed that she was pregnant while she was romantically linked with three men: Michael Tell, Desi Arnaz, Jr., and John Astin, who she ended up marrying and would adopt her son, Sean Astin. Patty long believed Desi Arnaz was Sean's biological father, but in the 90s, Sean took a blood test proving that Michael Tell had been his biological father. However, he still thinks of all three men, along with her final husband Michael Pearce, as his fathers.
- DNA testing companies that allow people to find out their ancestry (23andme, Ancestry.com, etc.) have had enough people find out that their father isn't biologically related to them that 23andme issues a warning about it: "Unexpected relationships may be identified that could affect you and your family."
- B.B. King had at least fifteen acknowledged children throughout his lifetime, although both of his marriages were childless. When writing his autobiography, his ghostwriter discovered King had been informed he would most likely never be able to father children. King took it rather philosophically, and never did anything to suggest the children were not his.
- This r/AskReddit post has a few examples: Doctors and nurses of Reddit, have you ever witnessed a couple have a child that was obviously not the father's? If so, what happened?
- The Roman Empire
- Drusus the Elder, the adoptive and step-son of Augustus, was rumored to be his biological son rather than being the son of Tiberius Claudius Nero. This is down to Livia being pregnant around the time she divorced her old husband and married Augustus. While no real evidence was made, Drusus' son Emperor Claudius encouraged it because it'd give him a clearer link to Augustus.
- Subverted with Augustus's daughter Julia, whose children reportedly all took after her husband despite her decidedly nonexclusive personal life. She's said to have explained "I take on a passenger only when the ship's hold is full," thus also averting No Pregger Sex.
- Because of the claims that his mother was an adulteress and how different he was to his father, there were rumors that Commodus was fathered by someone other than his father Emperor Marcus Aurelius. In reality there's little evidence that his mother was unfaithful and he was probably Marcus's son anyway.
- Defied by this lovely former couple from Craigslist. They'd been dating for 4 months, and the woman got pregnant, despite their always using condoms. Unbeknownst to her, her boyfriend had gotten a vasectomy several months before they'd even met, so there was no way that the baby was his. (The condoms were for STI protection, not birth control.) She wanted to keep the baby, and tried to trap him into a Shotgun Wedding. He got notarized documents from his doctor, and notarized copies of lab results showing that he was "shooting blanks." Then, he went over to her place to tell her that he was going to marry her and help raise "their" child...and showed her the documentation. (Needless to say, they did not end up getting married, or continuing their relationship.) After the breakup, the rumor was that the ex-girlfriend did end up carrying to term, and that the baby's biological father was some guy in a band.