Many family secrets are kept both in Real Life and fictionland. Orphans are one of the most popular character tropes, especially ones which turn out not to be orphans; the most famous example of this is the Luke, I Am Your Father situation wherein a thought-to-be unrelated character (often a villain, usually the Big Bad or The Dragon) turns out to be The Hero's parent. But sometimes these parents are hidden closer to home; sometimes, for some reason or other, they pose as a different relative — aunt, uncle, etc. and play a part in bringing up the child.
The most typical example of the trope would be an "older sister" who is actually a mother and "parents" who are really grandparents, a situation that was frequently Truth in Television before premarital sex and childrearing out-of-wedlock were destigmatized. (See the Real Life section for more historical detail.) In fiction set in the past, this may still be the reason for the Switcheroo. In contemporary society, the damage done by forcing the family to lie to the child and to the outside world is generally seen as much worse than an admitted out-of-wedlock birth—even if the child is being raised by their grandparents or other relatives, they will know who their birth mother is. Contemporary Switcheroos (both in real life and in fiction) are likely to be concealing a much darker and more potentially damaging family secret, such as a pregnancy caused by rape or incest.
What effect this has on the child varies from story to story, and how The Reveal happens. It should be pointed out that sometimes the focus of the story is the "older sister" and not the child, or the focus is on both equally.
See also: Luke, I Am Your Father, Luke, You Are My Father, and Stigmatic Pregnancy Euphemism. Compare Cain and Abel and Seth.
Note that this trope covers any Switcheroo, not just a mother claiming to be the character's sister. There are no inversions or gender-inversions.
In Another, twin sisters Mitsuyo Fujioka and Yukiyo Misaki both became pregnant. Mitsuyo gave birth to twin girls, Mei and Misaki, but Yukiyo miscarried and fell into depression. Meanwhile, the Fujioka family was having financial problems from caring for two children, so when the twins were two, they sent Mei to the Misaki family. They presumably sent Mei because if they sent Misaki, her name would be Misaki Misaki. The switch was kept secret for several years, but their grandmother slipped up one day. The girls began to secretly spend time together, but sadly, Misaki died a few years later.
In Digimon Adventure, Izzy/Koushirou Izumi overheard his parents talking one night about how they were not his biological parents, and they wanted him to remain ignorant of this until he was older. After a period of angsting about it he found out that his father was in fact his biological father's cousin, and that they had adopted him after his birth parents had died since they had recently lost a child of their own, and the family reconciles.
In Wildstorm comics' Wild CATS it was recently revealed that Zealot, who has looked out for her 'little sister' Savant since she was born, is actually Savant's mother. (And that Majestic was her father). However the Reset Button was pushed on the entire title the issue after this was revealed, so God only knows if it's still in-continuity.
Subverted in Transmetropolitan. Not only is the child entirely unwanted when it shows up - it also has no head, which fails to surprise anyone who knows the alleged father. And then it turns out to be a walking humanoid bomb.
Kelly O'Hare, title character of the 1983 (or so) comic Cutey Bunny has a dependent, Taffy, who both have enough youthful appearance to have characters remark: 'sister, huh...?'
This was one of the origin storiesnote Post-Crisis, pre-Superman: Birthright in the Superman legacy, that the Kent farm was cutoff from the rest of Smallville by a long snowstorm and it was during this time that Martha was to have given birth to Clark. The same story also states that Martha had suffered several miscarriages beforehand so the neighbors wouldn't have been suspicious if they hadn't publicly talked about the alleged pregnancy.
In the Hellblazer spinoff comic Lady Constantine, Johanna Constantine travels with her "little brother" Mouse, who's actually a girl posing as a boy. Johanna's reason for the disguise is that "bad things happen to little girls on the streets of London"... foreshadowing the reveal that Mouse is actually Johanna's daughter, and implying that the pregnancy was the result of rape.
Has occasionally cropped up in Glee fics, after Matt Bomer was cast as Cooper, Blaine's ambiguously aged older brother.
Alexandra Quick has Alex herself. Her mother, Claudia, is actually her oldest sister, who walked away from the wizard world. Her real mother is Hecate Grimm, who unfortunately suffers from amnesia so severe that her sister, Lilith, turned her into a cat, which has allowed Hecate to live a moderately decent life.
This is brought up in the middle of Curse of the Werepony, where it is explained that Sweetie Belle is Rarity's biological daughter, and their "parents" are actually cousins of Rarity's real parents, who disowned her.
The same setup is shown in "Dear Sweetie Belle", though their "parents" really are Rarity's parents in this one.
Chinatown, though here they were both sisters and mother and daughter; the father, Noah Cross had raped his daughter, and she gave birth to a girl.
Shara: A teenage girl's mother tells her she's actually her aunt.
In Digging to China, the protagonist learns that her sister is really her mother after her grandmother (who she thought was her mother) dies.
In the book and film versions of Devil In A Blue Dress, White Daphne and Black Frank are assumed to be lovers when they are spotted meeting in secret. In reality they are half-siblings, sharing the same mother but with different fathers.
In Jumping the Broom, Sabrina, the protagonist, learns that her Aunt Geneva is actually her mother, having become pregnant as a teen and abandoned by a man who turned out to be married. Sabrina was adopted by Geneva's older sister Claudine and her husband.
In the 1979 Superman movie, Martha Kent suggests that she and Jonathan tell people that the baby boy they found was "a child of my cousin's...and just now orphaned."
In Jenny, Juno, Jenny's older sister suggests that they hide Jenny until she's had her baby, and then send it to be raised by a relative in America who recently gave birth. The relative can then claim to have had twins. The mother dismisses the idea as too much like a soap opera.
Russian comedy Shirly-Myrly is this trope taken to the extreme. Not only the main character, Krolikov, was raised by his aunt pretending to be his mother, but he also has a number of twin brothers who are also raised by various stepmothers. Also played for An Aesop, since Krolikov is an outspoken anti-semit early in the film, so when his birth father revealed to have been a jew, it strikes him worse than the earlier revalation he's actually a stepchild. Each of his twins also believed himself to be a descendant of some other ethnic group, such as Jews, Romani or African. They all have some racist sentiment against each other, which they have to overcome upon learing they are brothers and actually hail from a very mixed common descent.
In His Dark Materials Lyra's "Uncle" Lord Asriel was actually Lyra's father, her mother was Mrs. Coulter, making Lyra have a case of both this trope and Luke, I Am Your Father. This masquerade was to cover up an affair.
A slightly confusing example occurs in the novel A Yellow Raft In Blue Water: Christine is really the daughter of Ida's father and her aunt Clara on her mother's side, making her technically Ida's three-quarter sister (or something like that) but Christine was raised to believe she was Ida's in order to cover up the affair that created her. This is made even weirder by Ida's insistence that Christine call her "Aunt Ida." In the end only Ida and the reader knows this.
On a similar line, in 'Travels with my Aunt', the aunt turned out to the mother, while his 'mother' really was his aunt taking responsibility for her sister's mistake.
In A Suitable BoySaeeda Bai was raped at a young age by the Nawab Sahib of Baitar, resulting in a daughter, Tasneem. To protect the Nawab Sahib's reputation, they pretend Tasneem is Saeeda's sister. This comes back to haunt the Nawab Sahib when his son falls in love with Tasneem.
Implied in A Song of Ice and Fire: Everybody believes that Eddard Stark is Jon Snow's father whereas there is a lot of evidence that he is in fact his uncle. The Reveal remains to be seen, though.
This is one of the main plot points in Catherine Forde's Fat Boy SwimJim Kelly's Aunt Pol is his mother, and "Mum" is his grandmother.
A very traditional example: in the first book of the Stravaganza series, Arianna discovers that her "parents" are actually her aunt and uncle, and her mother is really the Duchessa of Belezza.
In the Maeve Binchy book Evening Class, a character is stunned to realize that her older sister is actually her mother. Ironically, she is told this by someone who was completely unaware of the secret—she merely saw the two together and assumed. When the girl confronts her "sister" and asks her point blank if she's her mother, the woman's silence is of course, her answer. Despite the Irish/Catholic setting of Binchy's books and the time period the book is set during, it's revealed that this was NOT done out of shame because of the situation—the woman explains that her mother's reaction to her pregnancy was to simply say "won't it be grand to have another baby around here", thus revealing that she had her family's unconditional love and support.
In Torey L. Hayden's Beautiful Child, it is revealed that one of a poor mother's large brood is actually the product of her boyfriend and her mentally retarded teen daughter. The child herself is unaware of this. This is a true story.
When visiting her "older sister" who is comatose in hospital, Kit, the main character of Maureen McCarthy's When You Wake and Find Me Gone, receives a letter written by her "sister" which reveals that she is really Kit's mother and that her father is somewhere in Ireland.
In To Hear a Nightingale by Charlotte Bingham, Cassie grows up being abused by her grandmother and told what a slut her mother was. When her grandmother dies she finds out that her "grandmother" was really her mother. The woman had had an affair when in her 40s and hadn't ever accepted having a child. This nearly destroys Cassie.
Maximum Ride: Jeb Batchelder is Max's biological father as well as her guardian, and Dr. Martinez is her biological mother.
In Shanghai Girls, which takes place in the 1920's, May's daughter is raised by her sister Pearl as her child, since even though May was married, she had never had sex with her husband.
In the Wildflowers series by V. C. Andrews, Cat is raised as her sister Geraldine's daughter. She is initially led to believe that she is Geraldine's biological daughter, then her adoptive daughter. It turns out neither is true - Geraldine's mother gave birth to Cat, and they are half-sisters.
In the Cutler series by the same author, Lillian discovers that her mother Georgia is actually her aunt - Lillian's birth mother was Georgia's sister who died shortly after Lillian was born. Later, when Lillian is raped and gives birth to Charlotte, the family pretends that Georgia is Charlotte's mother too.
Chris Crutcher did this in two of his stories. In Deadline, Dallas is really the mother of her younger brother; this is kept a secret because he was the result of being raped by her uncle at a young age. In Ironman,Stacy Ryder's younger brother is really her and Preston's son.
Jayfeather, Lionblaze, and Hollyleaf of the Warrior Cats series are raised as Squirrelfight's and Brambleclaw's kits. However, Leafpool, the sister of Squirrelflight and Jayfeather's mentor is their real mother. When this is revealed to the three, Hollyleaf doesn't take it well.
In Ishq And Mushq, Sarna's illegitimate daughter, Nina, was raised by Sarna's mother as her own daughter.
In Amy Tan's novel The Bonesetter's Daughter, the protagonist LuLing is raised by her biological father's brother and his wife and her real parents are her "babysitter" Precious Auntie, the titular character, and her murdered fiance. This explains why her "younger sister"/cousin GaoLing is pampered like an eldest daughter.
In the Janie series, the titular character is raised by two people she believes are her parents. As it turns out they believe they are actually her grandparents and she is the daughter of their estranged daughter, when in reality, both are incorrect, and she was actually kidnapped from a third, unrelated family.
The Doctor Who two-parter "The Empty Child"/"The Doctor Dances" involved a young woman who was haunted by a little boy zombified-by-nanotech, who turned out to be her son. He was only healed of his zombification after Nancy admitted to him that she was his mother, and the nanogenes recognized the literal 'mother genes' and heal him and everyone else based on their new knowledge. Prior to this he'd been walking around spreading The Virus and calling out "Are You My Mummy?" (and being pretty damned creepy while doing so), hence the former trope name.
Spinoff Torchwood gets into the act as well. Captain Jack Harkness (who was introduced in the above Doctor Who two-parter, and who has since become immortal) ends up masquerading as his daughter's "brother" once she grows up - she knows, but her son (Jack's "nephew"/grandson) doesn't.
Desperate Housewives : Bree hides the pregnancy of her teenage girl and pretends to be the mother of her grandson.
EastEnders has the following famous interchange between the Slater "sisters" (though The Reveal for the audience had happened a few months before, this was when Zoe found out). This was due to rape, Kat had been raped by her uncle at 13.
Zoe Slater: You can't tell me what to do, you ain't my muvver! Kat Slater: (Zoe's "sister") Yes I am!
In Princess Returning Pearl, for a long time, it was kept a secret that Xiao Jian was Xiao Yan Ziís brother, and the person who basically caused their entire familyís death is Qian Long, who is not only Xiao Yan Ziís adoptive father but also the father of her sworn sister and best friend, and of her fiancť. There is a big reveal eventually that basically accummulates to become a Drama Bomb.
Similarly on Playing the Field, a BBC TV drama series about a women's football team. It fairly quickly wound up as a series about sex, relationships, and Aren't Men Awful, and this trope naturally turned up in due course: two of the team members were actually mother and daughter and not sisters as the younger one thought. (The mother wasn't raped, except in the statutory sense; she had an under-age but fully consensual affair with a much older man, and refused to identify him when she fell pregnant. Naturally, he's about the place in the series too.)
At the end of the first season finale of Pushing Daisies, Chuck's aunt Lily claims to be Chuck's mother. Chuck herself becomes aware of this early in season 2.
In the final season of The Sopranos, it is revealed that Paulie Walnuts has been raised by his aunt his entire life, because his mother was a nun who broke her vow of chastity with an American soldier.
Subverted in Rome. When Niobe's husband comes back after years of absence to see her holding a baby she has some explaining to do. She claims it's the son of their 13 year old daughter. Given how well the secret was kept it seems they must have kept the neighbours in the dark too and planned the substitution from the start, or invoked this trope.
An episode of NUMB3RS revolving around a polygamist cult featured a pair of women who were sisters and mother and daughter (unknown to the daughter until some way into the episode).
The 1990 TV miniseries version of The Phantom of the Opera, with Charles Dance. In it, it is revealed that the operahouse's old manager is Erik's father, but he has pretended to be a more distant relative, 'out of cowardice'. Towards the end, he reveals the truth to Erik, who in a slight subversion says he'd known it, and wondered when he would tell the truth. The same thing happens in the Yeston-Kopit musical version, which had the same writer.
Oddly enough, played for laughs - sort of - in 30 Rock's Valentine's Day episode, as the capstone to the worst first date ever.
On Veronica Mars, Jackie's 'younger brother' is revealed to be her son—a fact he is not aware of, as he calls his grandmother 'mom'.
In the Australian soap Home and Away, Charlie is revealed to be Ruby's mother, born after Charlie was raped. Charlie's parents raised the baby as their daughter. When Ruby finds out, she goes ape about it, before finally forgiving Charlie for the deception.
A major arc on Moesha involves Dorian discovering that his uncle, Frank, is really his biological father, born from a relationship he had while he was separated from his first wife. His mother was thus really his aunt.
On The Parkers (a spin-off of Moesha, above), Nikki is shocked to discover (on a family trivia game show, no less) that she was adopted. Her biological mother turns out to be her aunt.
Original Law & Order had it in the episode "Merger" in 1999, where the teenaged murder victim was the daughter of the wealthy family's older child, and not a sister
In Neighbours, Lyn Scully discovered that her Aunt Valda was actually her mother, who had gotten pregnant with her at a young age and been forced by her family to give baby Lyn to her older, married sister.
Godiva's: A secondary character named Chantal shows up to stay with Simone, her estranged older sister. Turns out Simone is actually her mother. (Coincidentally, Simone "deflowers" a young busboy named TJ in a much earlier episode — the same TJ that Chantal now starts dating.)
Frasier discussed this trope when Roz got pregnant and decided to raise her kid on her own.
On The Vampire Diaries, Elena learns that her uncle is actually her biological father; she was born when he was a teenager, and after the mother left town, he gave his daughter to his much-older brother and his supposedly infertile wife to raise as their own child.
On One Life to Live, Destiny Evans was raised by her paternal grandparents, but believed they were her parents. She later learned that her real father was her "older brother" Greg, who accidentally killed her mother Charlene, the girlfriend of his brother Shaun, and then gave Destiny to his parents to raise.
On General Hospital it was revealed that Claudia Zacchara was not actually Johnny Zacchara's sister but his mother, making Anthony Zacchara his grandfather (his real father was Gino).
In Time Gentlemen Please, it is greatly implied that the Guv's "Uncle" Barry is actually his real father.
In Emmerdale Rishi Sharma decides to pretend he's the father of his son Jai's child with Rachel Brickle to save Jai's marriage his wife Charity by covering up the fact that Jai had a brief one night stand affair with Rachel. In this case however it doesn't take all of the stigma away from the situation, given that the child is still known to be the result of an extra-martial one night stand anyway, but it just means that as Rishi's marriage is already in the gutter anyway he thought it would be better to protect his son Jai.
In Lab Rats, Adam, Bree and Chase are under the impression that Donald is their biological dad. They find out that he's really their uncle who adopted them because their real dad, his brother Douglas, created them to be weapons. They also find out that Marcus, who they thought was just a classmate turned enemy, is really their brother as Douglas is his father too.
In one episode of 2point4 Children, Rona's about to lose her council house unless she can provide her birth certificate to have the tenancy transferred to her as the daughter of the previous tenant. The birth certificate forces "Aunt" Pearl to reveal that she is Rona's real mother, but Rona grew up with Pearl's childless sister and brother-in-law since Pearl wasn't married at the time.
Justified: Kendal Crowe is introduced as the youngest brother of the family; he's actually the son of his "sister" Wendy.
Top Girls by Caryl Churchill: Angie is really Marlene's daughter, but was raised as the daughter of Marlene's sister Joyce. Poignantly played upon in the last scene when Angie calls for her mother and Marlene responds "No, it's Aunt Marlene."
In Drowtales, it turns out that Ariel is not really Quain'tana's daughter, but is actually Mel'arnach's, who she's been raised to think of as a sister. And just to further complicate matters, Ariel's father is Zhor, a dark elf who was transformed into a frickin' giant spider.
Homestuck: Quite a few examples, due to ectobiology (i.e., cloning) and Time Travel mismatching generations and ages. Dave's older brother is actually his genetic father. Jade's grandfather is actually her genetic father. John's long-dead grandmother is his genetic mother and his father is actually his half-brother. Averted with Rose: Mom Lalonde IS her genetic mother. Ironically, Bro Strider is about the same age as Mom Lalonde, making it all the stranger that he tells Dave they're brothers instead of father and son.
And then after the scratch, we have the original kids swapped with their genetic parents. Jane Crocker was raised by Dad, who is now her genetic grandson. Jake was adopted by his genetic daughter, Jade, who called herself his grandmother. Dirk and Roxy refer to their genetic son and daughter respectively as older brother and mother. Timefuckingshenanigans.
In Dragon City, Beatrix's case is a little different. She and her "older sister" Erin traveled back in time to when Beatrix's egg was laid. It was at this point that Erin lays Beatrix's egg, though she ends up getting raised by their mother of that time period (who mistook it for one of her own eggs).
One episode of The Simpsons has Bart (pretending to be older) date a fourteen-year-old girl who turns out to be pregnant. After being assured he can't be the father ("Wow, you are only ten") he agrees to marry her anyway to hide the truth. When the girl's parents find out the mother announces that she's pregnant too, and the family (with sort of creepy cheerfulness) agree to pretend the mom has twins. It is therefore implied that The Reveal will occur some years later.
The Venture Bros. has the reveal that Dermott is the son of Rusty Venture and the fifteen-year-old president of his fanclub, and was raised by the mother of his biological mother.
Donna: This isn't going to be easy to hear... Rallo: Roberta's actually my mother? Donna: Don't ever say that again!
Up until the 1970s (when the Pill and legalized abortion became available and cohabitation became acceptable) it was common for young women pregnant out of wedlock to be "sent away" before they started to show and to give birth in secret. "Homes for wayward girls" were essentially private maternity wards where women were heavily pressured to give their children up for adoption (as long as they were white—at the time the adoption prospects for nonwhite babies were...pretty grim). Birth mothers might not even be allowed to see their babies before they were taken away to the adoptive parents. Faced with losing her child forever, it's not hard to see why a mother might prefer becoming an "older sister" who could still be part of the child's life. The Girls Who Went Away by Ann Fessler is a good source for those looking to learn more about maternity homes and forced adoption. While many children of young unwed mothers are still raised by their grandparents, it's much less common for families to bother concealing the underlying biological relationships.
Jack Nicholson's "older sister" was really his mother while the woman who was allegedly his mom was actually his grandmother. His real mother did it because she had sex with a man (both were unmarried) who ended up leaving her and she didn't want anyone to know that she was an unwed mother (both Nicholson's grandmother and mother died before he found out this family secret). In a height of coincidence, he learned this just as Chinatown — in which he starred — was about to open in theaters.
David Campbell. His real father was Jimmy Barnes, who would go on to become an Australian rock icon.
Ted Bundy suspected for years that his older sister was in fact his mother, finally learning it for a fact in 1969. Even worse, she might very well have been his sister after all, given the heavy, yet unproven speculation that he was the result of Parental Incest between her and his grandfather.
Lina Medina's (NSFW picture) first son, necessitated by her being the world's youngest mother at the age of 5. He found out when he was 10 and Lina was 16.
The Guinness Book of Records refuses to accept many well-known historical claims for "oldest mother to successfully carry a child to term" out of suspicion that they were examples of this trope.
Jaycee Lee Dugard's two daughters, (ages 15 and 11) by her rapist and kidnapper Phillip Garrido believed their whole lives that Jaycee was their older sister and that Garrido's wife was their mother. They had to find out the horrible truth after the police finally caught and arrested Garrido.
Upon the announcement of her candidacy for Vice-President of the United States in the 2008 elections, rumours began to circulate that Gov. Sarah Palin was actually the grandmother of her youngest son, and that his oldest sister was actually his mother. Subverted, as the rumours were soon proved completely unfounded. Her eldest daughter, Bristol, would later get pregnant out of wedlock, but the Palins decided to be public about it.
In the Middle Ages it was not unusual for popes to have illegitimate children (such as Pope Alexander VI's children, Cesare and Lucrezia Borgia) that they bestowed favors upon, although it was considered gauche to publicly acknowledge their paternity. Instead, they were referred to as "nephews" or "nieces" of the pope. This is the origin of the term "Nepotism".
In 1939, a then-5-year-old girl from Peru named Lina Medina was taken to the hospital for a tumor in her belly. During the examination, it turned out that she was pregnant (she had gone through puberty at an unusually early age). She gave birth via c-section to a young boy, but was told her whole life that he was her younger brother. It is not known who his father was; Lina's father was jailed on suspicion of incest, but he was released for lack of evidence, and Lina herself wouldn't say who had done this to her. She lived a pretty normal life otherwise, and later married and had another son (this time one that she actually knew was her son.)