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Royal Inbreeding

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"The royal bloodline isn't what it used to be; too much inter-marrying, I suppose. I always say when you reduce a family tree to a family bush, you just can't hide as much beneath it!"
Regent Virini, Babylon 5

Often, those of noble or royal birth are supposed to marry other nobles, typically in Arranged Marriages intended to secure alliances, but since there are so few of these people this frequently leads to marriages between cousins or similar relatives. Some even marry their siblings.

To qualify for this trope a family doesn't necessarily have to be literal royalty, but as long as they have sufficiently high status compared to the rest of their society and practice this mostly to "keep it in the family" with either money, powers that are In the Blood or other inheritable traits or possessions it still counts.

Oftentimes this is used to explain The Caligula, Royally Screwed Up, and It Runs in the Family. Might be used to justify a Single Line of Descent and Lookalike Lovers. Inbred and Evil has an interesting relationship to this trope, as the attitudes that were used to justify inbreeding among nobles were pretty much the inverse, but it's also one of many allegations used to prove that Aristocrats Are Evil. There's some surprising parallelism to its Opposite Trope, Hillbilly Incest. Incest is associated with the extreme upper and lower classes, and almost never with the middle class.

Related to Divine Incest. Since incest is commonly associated with the gods, doing it as humans is to take on the trappings of the gods. Gods are above the rules, and so too are royals. Or maybe the royals are outright God Emperors.

This is Truth in Television, primarily associated with Ancient Egyptians, Incas, and Hawaiians. It served as a tool to keep land and other forms of inherited wealth in the same family or to renew alliances.

See also Incest Standards Are Relative, a broader look at what counts as incest, and thus taboo, across cultures, time periods and social strata.


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    Anime & Manga 
  • Berserk: According to the king's brother Count Julius, his son was to marry the king's daughter Charlotte when both came of age. This ends up not happening when Guts is ordered by Griffith to assassinate Julius and accidentally kills Julius's son in the process when he reflexively attacks upon realizing someone's seen him.
  • Though there are no actual marriages between family (barring Suzaku being betrothed to his cousin Kaguya as a child), Code Geass contains a lot of Incest Subtext between the Britannian royal family. As a child, Lelouch was fought over by Euphemia (his half-sister) and Nunnally (his full-sister), and it wasn't presumably childish innocence as Lelouch mentions that he considered Euphemia his first love. At the end of R2, when Nunnally realizes the reach of Lelouch's Thanatos Gambit, she tells him so via what sounds exactly like an Anguished Declaration of Love.
  • The Irregular at Magic High School uses this trope as a sudden plot twist in the 16th volume when it becomes clear that Tatsuya should become the future husband of his own sister so that his unique abilities remain forever in the clan. So, as his sister is a perfect Designer Baby, their siblings' marriage will not be dangerous for their children and eventually give their clan even stronger offspring than if she married another person. Although the rest of the magical world as a whole averted it (as mentioned, even a marriage between cousins is considered undesirable due to possible genetic problems), we learn that Yotsuba is not the first clan that started experimenting with incest thanks to new opportunities offered by genetic engineering.
  • This is implied in Naruto with several ninja clans. Sasuke's parents both look like they could have been Uchiha prior to marriage (though an anime filler implies that Mikoto might not be naturally an Uchiha, as she and her husband have to travel to visit her parents), Hinata's mother is shown in the anime and looks like a Hyuga (though the fact her eyes are closed means it's impossible to tell for certain if she had the Byakugan or not), and Itachi mentions that he killed his lover during the Uchiha massacre. And given the extreme lengths the Hyuga went through to prevent outsiders from obtaining the Byakugan, it's highly likely they would've favored marriage within the clan. On a less canon and Played for Laughs side, Rock Lee's Springtime of Youth exaggerates Neji's Big Brother Instinct towards Hinata to outright Kissing Cousins, and Road to Ninja also features an alternate version of Neji that is perverted towards Hinata. Given the large size of both clans, it would be entirely possible for them to have "kept it in the clan" while still marrying fairly distant cousins rather than close relatives.
  • Apparently not uncommon in the Juraian royal family in Tenchi Muyo!, as Prince Yosho was engaged to his half-sister Ayeka prior to going AWOL (though it's suggested they didn't actually intend to go through with it and mostly arranged it to quiet potential objectors due to Yosho being mostly human, notably apparently no-one had a problem with the incest). As part of the Marry Them All solution to the main series' Love Dodecahedron, Tenchi could also potentially end up with Ayeka and/or Sasami, who technically speaking are his great-aunts.
    • Due to a truly Tangled Family Tree, in most continuities Tenchi is (potentially) related to all of his would-be love interests. Though characterising the exact relationship between Tenchi and Washuu and her family (Ryoko and more distantly, Mihoshi) is tricky. Short version, Washuu is the sister of Tsunami, who is undergoing a long-term fusion with Sasami, one of Tenchi's aforementioned great-aunts. So in a way, Washuu is Tenchi's great-aunt as well, genetically she is not since the relation is via fusion.
  • In Vampire Game, the royal family of Pheliosta is required by law to marry incestuously in order to keep the bloodline pure for King Phelios, who according to prophecy will be reborn as his own descendant a century after his death. Protagonist Ishtar, who hates most of her family and is in love with her decidedly non-royal bodyguard, is none too pleased about this.
  • In Vampire Knight pureblooded vampires are the equivalent of royalty within their communities and commonly marry within the family to maintain their status. It turns out that Yuuki's parents Juri and Haruka were brother and sister, and Juri's other brother Rido also had his eye on her.

    Comic Books 
  • Preacher: It turns out the Holy Grail is indeed the receptacle of Jesus' blood... meaning they're the organisation who've been making the original descendants of Jesus interbreed for nearly 2,000 years to keep his bloodline pure. The results are universally handicapped, deformed (the latest was born with eyes half the size of his head), and anything but divine... yet somehow less physically freaky than the family of one-eyed hillbillies Jessie met and befriended.
  • Sleepless: The trope gets Played With in the comic as different factions maneuver to get the eligible royals of Harbeny married off for their benefit:
    • Played Straight — Lord Helder pursues his cousin, Princess Rellen, once her father is made King of Harbeny and Rellen is made Crown Princess. Helder feels no attraction to her, but as the "second son of a lord's third daughter", he's desperate to marry into a ruling line (even if he'll only be Prince Consort). When King Surno learns of this, he dismisses the idea of his nephew Helder marrying Rellen as "the utmost ridiculousness."
    • Downplayed — King Surno wishes to have his nephew Lord Helder married to his niece Lady Poppy. Poppy is the daughter of Surno's brother, while Helder is Surno's nephew by marriage (the son of Surno's wife's sister). In this case, Poppy and Helder would have no blood relation (assuming Verato and Surno were not related to the Eldtish royalty that Surno married into).
    • Averted Although Poppy and Helder do marry, he is assassinated on their wedding night. Poppy is left free to pursue her romantic interest in the non-royal Sir Cyrenic.
  • The Greek gods have always been their rather inbred selves but the New 52 made Wonder Woman the result of inbreeding in the family. She is made the daughter of Hippolyta and Zeus while doing nothing to change Hippolyta's status as Ares' daughter, making Zeus Diana's father and great-grandfather and Ares Diana's grandfather and brother. Traditionally Wondy rather emphatically has no father, and this fan-disliked change to her origin was quickly done away with and discredited in Wonder Woman (Rebirth) until James Robinson brought it back to make a storyline centered on one of Diana's brothers from the New 52.
  • In the X-Wing Rogue Squadron, Rightfully Returning Princess Plourr Illo is surprised to see her second cousin Rial again, and dismayed by his belief that they'll go along with the old Arranged Marriage set up when they were children. Her bloodline has in-bred and been tampered with to keep it "pure" (including with couples more closely related than just second cousins), which sometimes has disastrous results. Such as Plourr's murderously psychotic brother, who she killed while they were still children in order to stop his own killing spree.

    Fan Works 
  • Defied by the Romulan noble class, according to Heis'he Ri'nanovai. Due to their low starting population (only seven of the original eighteen colony ships survived the Journey from Vulcan to colonize Romulus) and tendency to Altar Diplomacy, Romulan Blue Bloods would be vulnerable to this were it not for gene-maps kept by the clans to avoid such mishaps.
  • Though as far as we know it's not the case in the original show (aside from the princess being slated to marry her cousin), Berserk Abridged cites this as the reason the Midland Royal family is as Royally Screwed Up as it is, and why Princess Charlotte turned out the way she did, with a regal bearing like a cow looking at an oncoming train.
  • In the My Little Pony: Friendship Is Magic fanfic Maternal Instinct, the royal family of the Changeling Kingdom, the House of Roachanov, has practiced inbreeding for hundreds of years. Because of this, many of the present-day members of the family have noticeable birth defects. Changelings normally have large numbers of children, but Queen Chrysalis' children have all died from inbreeding-related birth defects or illness exacerbated by their weakened immune systems. Her only surviving daughter, Princess Pupa, is mentally handicapped and has a long list of health problems, including malformed legs and wings, scoliosis, and low white blood cell count.
  • In Little Fires, it's noted that ThunderClan has become very inbred. Most cats are related to one another somehow and they look a lot alike as well. This has resulted in several stillbirths and ill kittens. As a result, they've begun letting in cats from out of the Clan in order to bring in new blood.
  • In Never Been Bothered, it's noted that incestuous relationships are not unknown to occur between Arendelle royalty. However, sibling incest is unheard of. As a result, Anna and Elsa's same-gender, sibling incest relationship caused the worst scandal in their country's history, forcing the two to flee far away.
  • New Tamaran: Starfire unashamedly admits to coming from eight generations of brother-sister marriage; one could imply that Blackfire’s “defects” are a result of this.
  • Their Bond:
    • Historians believe that Queen Eldora had children with her brother Kelen. Kelen reportedly resembled Eldora's husband so it went under the radar. It's been noted that Eldora's husband likely consented to the relationship as he preferred the maid over his legal wife (and had kids of his own with the maid).
    • Queen Zelda's cousin, Prince Daltus of Lucrum, tries to get her to marry him. Zelda is offended by the audacity of his offer, as she had only recently announced her engagement to Impa.
  • In So We'd Both Be Free, Ozai mentions he wants to continue his bloodline. His daughter Azula originally believes he's going to order her into an Arranged Marriage, but he instead impregnates her himself.
  • Nala: My Father's Madness:
    • Scar is king of the Pridelands. He declares an Arranged Marriage between his daughter Nala and her younger half-brother Nuka. In the case that Nala refuses, he'll have her killed and instead marry Nuka to his full-blooded younger sister Vitani. Neither marriages go through because Scar is killed soon afterwards.
    • Though it was unknown to most of the pride (including Simba's parents and Nala's father) until adulthood, Nala and Simba are cousins who were in an Arranged Marriage. They end up marrying and becoming the queen and king of the Pridelands together.
  • It's implied that Zelda is RH negative in Divorced because the Hyrulian royal family often inbreeds to varying degrees.
  • In Royal Privilege, Lelouch impregnates his mother Marianne and half-sister Guinevere with plans to impregnate several more of the royal family, including his sister Nunnally. To make things really complicated, Marianne discovers that she's Charles' bastard with his own mother*
  • It's not quite just one family, but the increased emphasis — and legal enforcement — of blood purity in The Rigel Black Chronicles has resulted in a large percentage of the population being "hyper-pure", with not just all-magical grandparents but many generations previous. This results in very orderly and controlled magic, unlike the wilder and unpredictable magic of first-generation magic-users, but Hermione's research shows that it is also the source of the Fade, a lethal disorder affecting second and succeeding children in hyper-pure families, leading to a looming population implosion if measures are not taken.

    Films — Live-Action 
  • Gladiator: Emperor Commodus indicates that he intends to force his sister Lucilla to become his concubine and carry his child because he is obsessed with creating a "pure-blooded" dynasty. He's killed before he can put it into action, though. This is some serious Artistic License – History, since aside from giving Commodus a dose of Historical Villain Upgrade, the historical Romans also had laws against incest (hence the slander against disliked emperors such as Caligula and Nero) and looked down on contemporaneous royal families like the Ptolemys for their habits.

  • The Accursed Kings: Just about every royal marries someone who's a cousin at least (though some are by marriage) since most of them are descended from Louis IX of France or his family.
    • Because so many marriages among nobility are cousins, Louis X can't use it as a way to get his marriage to Marguerite de Bourgogne annulled and has to use more dramatic measures that lead to tragedy for France and England.
    • Charles de Valois marries off his nephew (brother's son) Louis X to Clemence of Hungary (daughter of his brother-in-law). The usual consequences of inbreeding aren't seen since the child's Body Double dies a few days old of poison.
  • Not strictly royal, but the marriage practices of the Uplands are like this in Annals of the Western Shore. The brantors (local chieftains, basically) often arrange marriages between cousins to keep from diluting the family's magic power and ensure a strongly gifted heir.
  • Babar, King of the Elephants in Jean de Bruhhoff's children's books is Happily Married to his cousin Celeste.
  • Averted in A Brother's Price. One of the princesses says that she wouldn't mind marrying her cousin if she absolutely must marry someone, but her sister points out that he is too close in blood (while admitting that he'd otherwise be a good choice).
  • Chronicles of the Kencyrath: The Knorth, the royal house of the Kencyrath, has a long tradition of inbreeding to keep the bloodlines pure in order to honor a rather vague divine mandate. Twin marriages particularly were a tradition… at least until a particularly bad couple, who were to thank for two-thirds of their people being destroyed. After that, twin marriages acquired some... messy connotations and they stopped those. But kept on with the other kinds of inbreeding.
  • The Ciaphas Cain series partially blames the overall incompetence of much of the Imperial aristocracy (including the majority of planetary governors we meet) on an excess of inbreeding.
  • Discworld:
    • In Pyramids, the High Priest Dios suggests that newly-crowned pharaoh Teppic marry any available female relative. Of course, Teppic's kingdom is the Discworld's version of Ancient Egypt. His potential Love Interest, Ptraci, turns out to be his half-sister, and it’s left a little ambiguous at the end whether this proves to be an insurmountable obstacle for their relationship - though while Ptraci isn't bothered, Teppic is.
    • Parodied in Feet of Clay, where it's mentioned that in the city of Genua, the royal lines died out "through interbreeding so intensively that the last king kept trying to breed with himself".
  • A few examples in the Dune universe. Though mostly intended as eugenics.
    • Dune: The Bene Gesserit intended for Jessica to bear a daughter that would be mated to her cousin Feyd-Rautha as part of their Super Breeding Program, but she bore a son instead.
    • Children of Dune: Leto II symbolically married his sister Ghanima, though at that point he was physically unable to have sex so he had Prince Farad'n Corrino (who would be a very distant cousin) sire her children.
    • God-Emperor of Dune: Over the 3,500 years Leto II controlled the Bene Gesserit breeding program, he mated several of Duncan Idaho's clones with his sister's descendants. While Duncan himself was genetically unrelated to the Atreides family, this obviously became less and less true every time one of his clones fathered a new child.
  • In Everworld, the Pharaohs of Everworld-Egypt are so inbred that the last twelve rulers have been mentally retarded. That, combined with the gods' total apathy to anything but ritual, has led to the entire country stagnating until the dwarves and the Amazons were able to take over.
  • The Hands of the Emperor: The imperial family of Astandalas was prone to that, with cousins marrying cousins and even siblings marrying each other to keep the bloodline pure, which lead to some horrifying inbreeding:
    • The current (and last) emperor Artorin's parents had a child each year for as long as they could (he was born in the third year of their marriage, his sister Melissa ten years later), and except for these two, not one sibling survived their first hundred days.
    • Their cousin Shallyr - son of the former emperor and heir to the throne whose parents were also closely related - was physically okay, but cruel and stark raving mad. He was apparently so crazy that he either jumped off a balcony on his own account or somebody magically forced him to do so to have literally anybody else inherit the throne.
  • In James Michener's Hawaii, the Christian missionaries to Hawaii are appalled by the alii's (Hawaiian nobility) custom of inbreeding. At the time of arrival, the local alii is Malama who's Happily Married to her brother Kelolo. While the missionaries do object to this, it's also "grandfathered in" in a sense because they've already been married for decades. When Malama and Kelolo's children, Keoki and Noelani, are wed after the arrival of the Christians, Reverend Abner Hale is even more upset. He has the following conversation with a fellow missionary, John Whipple. Whipple has relaxed his views about a lot of things since arriving in Hawaii and Hale thinks he's Going Native.
    John Whipple: I've been thinking about it a great deal. What's so dreadful about it? Now really, don't quote me incidents from the Bible. Just tell me.
    Abner Hale: It's abhorrent and unnatural.
    John Whipple: What's really so abhorrent about it?
    Abner Hale: Every civilized society…
    John Whipple: Damn it, Abner, every time you start an answer that way I know it's going to be irrelevant. Two of the most completely civilized societies we've ever had were the Egyptians and the Incas. Now, no Egyptian king was ever allowed to marry anybody but his sister, and if I can believe what I've heard, the same was true of the Incas. They prospered. As a matter of fact, it's not a bad system, scientifically. That is, if you're willing to kill off ruthlessly any children with marked defects, and apparently the Egyptians, the Incas, and the Hawaiians were willing to do so. Have you ever seen a handsomer group of people than the alii?
  • In "The Fall of the House of Usher", it's noted that the Usher family tree is a straight line. This leads many readers to suspect an Incest Subtext in the relation between Madeleine and Roderick Usher.
  • Harry Potter:
    • The wizarding world doesn't have royalty, but certain pureblood wizards consider themselves the next best thing and keep their magical ancestry "pure" by marrying their cousins. The Malfoys, despite being unashamed blood supremacists, are smart enough not to practise inbreeding and will readily marry half-bloods if necessary.
    • The Gaunts are noted to have become increasingly erratic, violent, unintelligent, and magically untalented as the generations passed and their habit of marrying cousins caught up with them until irony hit and their last descendant, Tom Riddle (a.k.a. Voldemort), got an infusion of muggle DNA through his father and grew up to become one of the most brilliant and talented wizards of the modern era. Sadly this also included all the sociopathy that came from both sides of his gene pool.
    • Despite this, however, the series hasn't actually provided an example of an outright incestuous couple; the closest are Sirius' parents Orion and Walburga, who were second cousins, something that is not worth batting an eyelid in Europe. The Gaunts are mentioned to practise inbreeding, but we have no detailed genealogy to base this claim on.
  • A non-royal example in Andrey Livadny's The History of the Galaxy series. The St. Ivo family runs Galactic Cybersystems, the largest MegaCorp in history. The founder Erlk St. Ivo marries his cousin Liza to maintain the secrecy of the corporate HQ and R&D center. Deciding to continue the tradition, they had a son and a daughter, deliberately modifying their DNA so that they weren't genetically related. Each subsequent generation continued this, until the birth of André St. Ivo, whose intelligence level was far below normal (despite the genetic modifications). Deciding to break tradition and infuse the family with "fresh" blood, André's parents did not have a second child. He ended up marrying a smart young woman named Theia Mitchell. Due to her husband's inability to run a corporation, Theia ended up doing his job. Resentful, he had an assassin shoot her and then got a bunch of Mad Scientists to turn her into his sex slave, keeping her in stasis until he "used" her the next time. Due to all this inbreeding, André and Theia's sons Aramant and John ended up looking like André and Erlik, respectively. In the first case, this proved Aramant's undoing. After he found his mother in stasis and thawed her out, she assumed he was his father and killed him. John was mortally wounded and had his consciousness copied onto an android, all of whom look like Erlik (and, therefore, John).
  • Discussed and deliberately averted by the House of Winton, the royal family of Manticore in the Honor Harrington series. The heir to the throne is required by law to marry a commoner, both to avoid the inbreeding issues that despite the availability of 41st-century medical technology still tend to crop up in other aristocratic families and to keep the eventual ruler a bit more grounded.
  • In the second trilogy of Kushiel's Legacy Imriel de la Courcel falls in love with and eventually marries Princess Sidonie de la Courcel. Imriel is the son of Sidonie's great-uncle, making them first cousins once removed.
  • In A Legacy of Light, Tutankhamun and Ankhesenamun were married as children to maintain the royal bloodline.
  • Charles Stross's The Merchant Princes Series: The world-walking gene is recessive, so the old women of the Clan arrange marriages between cousins to keep the power in the family while preventing too-close inbreeding. The Clan also did manage to interbreed with the royal family at one point, but a genetic condition latent within the Clan ended up creating a retarded prince. The power of the "old bitches'" conspiracy and the cross with the royal family drives much of the plot of the third and later books.
  • Merry Gentry says this is a major problem with the fey due to immortality: they don't bother checking genealogical records or they'd know that their current paramour is a sibling born centuries apart. She herself has problems due to both her cousin (prince of the Unseelie Court) and her uncle (king of the Seelie Court) wishing to make her the mother of their children.
  • A Song of Ice and Fire:
    • The Targaryen dynasty wed brother to sister (not as often as you'd think, but likely more often than you want to imagine), first cousin to first cousin (most common, though not considered incestuous by Westerosi standards), or even uncle to niece (occasional) for centuries, which is often blamed in-universe for their tendency to produce the odd mad king (mainly by those very strongly of the Faith and rather biased on the whole issue). It got to the point that Daenerys (the series's most prominent Targaryen) only has two great-grandparents rather than eight because her parents and grandparents were brothers and sisters. It's suggested that the Targaryens have some sort of strengthened genes because they are, for the most part, physically sound, whereas the extent of such inbreeding would be genetically disastrous if it is practiced in real life (Daenerys is more inbred than the infamous Charles II of Spain). That said, many Targaryen kings did have to contend with higher-than-average rates of infertility and stillbirths, and plumbing the depths of Targaryen history will reveal more than a fair amount of royal children born with extra toes, webbed fingers, and scales… although that might also indicate that their claims to be "blood of the dragon," which such practices were meant to preserve, were Not Hyperbole.
    • Cersei and Jaime Lannister are twins who secretly have an affair. They have three kids. The good news: the younger two are sweet kids, and seemingly okay! The bad news: The eldest is Joffrey Baratheon, who starts a three-way civil war with two secessions. Jaime and Cersei tried to justify their relationship by citing the Targaryen practice, but both felt great pangs of guilt wondering if their sin led to their thoroughly rotten eldest. Also of note is that Cersei and Jaime's parents were first cousins who were both born with the name Lannister, although first cousin marriage is unremarkable in Westeros and isn't considered incest. Ned Stark's parents were first cousins once removed who were both born with the name Stark as well.
  • The Masters from The Stone Dance of the Chameleon place such a high value on blood purity that brother/sister, mother/son and father/daughter marriages are extremely common in the imperial family.
  • In Larry Niven's Svetz stories, the world is ruled by a hereditary Secretary-General. Centuries of inbreeding have produced a feeble-minded and childish occupant of that office.
  • In Tales of the Branion Realm, several pages are devoted to explaining how an exiled member of the royal family, over the course of about 75 years, managed to tie his bloodline back into the ruling line — by marrying his cousin, having their children marry second cousins, and having their grandchildren marry third cousins — one of whom is the current monarch. His child inherits the powers of four different septs of the dynasty in one go.
  • Discussed in the third book of The War Gods series, where one man mentions that some of the people in service to Baron Tellian (whose domain is large enough to be considered a duchy were he any nationality but Sothoii, which has no levels of nobility between 'Baron' and 'Royal') wish that he would marry his only child (Who, being female, cannot inherit directly, instead, passing her claim to her father's lands to her eventual husband) to his nephew Trinial. The man he's talking to says that this would never be permitted as they were first cousins. The first man agrees but points out that people wishing that it could happen said a lot about Trinial's character (In the end, Leanna renounces her claim on her father's lands to get away from the politics, and Tellian makes Trinial his heir directly).
  • In Warrior Cats, the Clans set themselves apart from other cats, believing their social lifestyle superior and other, solitary cats to be 'rogues': untrustworthy, dishonorable, and dirty creatures to be driven off their land by force. The Clans display quite a few signs of inbreeding, such as an extremely high rate of stillbirths (generally at least one in every litter larger than three), low overall fertility (litters rarely larger than four, normal would be four or more), and conditions such as 'rex' coats, limb deformities, Klinefelter syndrome, epilepsy, and kinked tails.note  It is never directly stated, but their intolerance of outsiders and small founding population (which was itself derived from a small founding population) would naturally lead to incest and therefore inbreeding. It is telling that the modern SkyClan, who are almost all former pets and ex-rogues, display almost none of these problems. One went deaf, but that's about it.

    Live-Action TV 
  • Babylon 5: In the episode "Epiphanies" the late Emperor Cartagia's descent into madness is blamed on the royal family tree being reduced "to a family bush."
  • 30 Rock features a fictionalnote  "last of the Habsburgs" prince (played by Paul Reubens) who suffers very badly from this.
    • Another episode had a gag with Liz at a fancy party calling the rich people there out, except "for the really inbred WASPs"; one of them promptly thanks Liz (we think).
  • In Downton Abbey, Mary is engaged to her distant cousin Matthew. Since Mary's father Robert has no male children, Matthew will inherit his estate. By marrying Matthew, Mary's place at Downton would be secure, and Robert's grandchildren would remain in the line of succession.
  • The Empress: As in reality, Emperor Franz Joseph is planning to marry his maternal first cousin Helene. He is taken with and marries her younger sister Elisabeth instead.
  • Game of Thrones universe:
    • Game of Thrones:
      • The former Targaryen dynasty usually wed their siblings or cousins, including Daenerys' own parents. Her brother Viserys hints that he wants to carry on the tradition, but instead has her sold off as a bride to the horselord Khal Drago, hoping to use his forces to invade the Seven Kingdoms.
      • Cersei Lannister had earlier used the Targaryen example as a justification for her own illicit romance with her twin brother Jaime when Eddard Stark confronted her with the truth of her children's illegitimate heritage. The truth is buried for political purposes despite becoming an Open Secret, but once Cersei becomes Queen Regnant in her own right, it appears that she doesn't even feel the need to bother hiding it from her subjects anymore.
      • It turns out that, unknowingly, Jon and Daenerys are doing this, as biologically, the latter is the former's aunt, with Jon's father being confirmed to be Rhaegar Targaryen, who was Daenerys's elder brother. However, Jon puts a stop to it when he finds out and ends up killing Daenerys for unrelated reasons before any offspring can result.
    • House of the Dragon: As mentioned above, Tragaryens routinely practice incestuous pairing. King Viserys and Queen Aemma were cousins, Rhaenyra is their only surviving child, and she ends up marrying her own uncle Daemon.
  • In just the third episode of The Tudors Henry VII arranged a marriage between his daughter Mary and her mother's nephew the Holy Roman Emperor Charles V, though the engagement was called off later. Note that Charles and his aunt were Hapsburgs (see Real Life).

    Tabletop Games 
  • Ironclaw: Grey foxes, the ruling house of Calebria, often exhibit signs of inbreeding like hemophilia or color blindness, with rumors of more extreme traits like polydactyly. The novel Scars elaborates further: all grey foxes in Calebria are of House Rinaldi, and if they mate with the more common red foxes their offspring are usually red. The other major houses are the same species as most of their peasants so they have the option of legitimizing their bastards and adding some diversity to their gene pools.
  • Warhammer 40,000: The Navigator Houses, aka the Navis Nobilite, tend to act like aristocrats and have become so inbred over the millennia that most if not all of them have mutations other than their genetically engineered third eye (which is recessive, hence the inbreeding).
  • Warhammer Fantasy:
    • It's said that during the most decadent days of the Empire, the nobles were so inbred that mutations became commonplace. The Witch Hunters seem to have solved that problem though.
    • Sigvald the Magnificent, the champion of Slaanesh, is the son of a Norsca warlord and his sister (the warlord's, not Sigvald's). His "fondness for human flesh" caused his expulsion from the tribe, at which point Sigvald murdered him and went off into the Chaos Wastes.
  • Werewolf: The Apocalypse: The Silver Fangs suffered from inbreeding despite their biological requirement to outbreed (Werewolf/Werewolf pairings always result in the sterile and deformed Metis no matter how closely related the parents are). They managed this by being so proud that they disdained marrying any humans that weren't royalty. So not only did they severely limit their pool of potential partners, they also got all the Royally Screwed Up that resulted from previous inbreeding. Marrying into the Habsburg line was not very good for their genetic health.

  • In Elisabeth, as it was in Real Life, Franz Joseph (of the famous House of Habsburg) was intended to marry Duchess Hélène in Bavaria and ended up marrying her sister Elisabeth instead. The bride and groom were first cousins.
  • This trope drives the main plot and two subplots in Gilbert and Sullivan's H.M.S. Pinafore. Sir Joseph Porter, the First Lord of the Admiralty, boards the Pinafore to court Josephine, daughter of the ship's captain. However, seaport floozy Buttercup declares that, in her youth, she breastfed both Captain Corcoran and seaman Rackstraw, and inadvertently mixed up the two infants. Sir Joseph then declares that he cannot marry Josephine, as she is the daughter of a mere seaman, her charm and grace notwithstanding. This allows now-Captain Rackstraw to propose to Josephine, and demoted-to-seaman Corcoran to pursue Buttercup. Sir Joseph resigns himself to courting his cousin Hebe.
  • In A Man for All Seasons, the king tells Thomas More that he considers having married his dead brother's wife to be incest, despite them not being relatives by blood.

    Video Games 
  • Assassin's Creed: Brotherhood: Implied Brother–Sister Incest between Cesare and Lucrezia Borgia. Though not literal royalty, due to their father being the Pope they might as well be, and the whole Borgia clan is certainly Royally Screwed Up enough to qualify.
  • The Yayoi clan in BlazBlue is one of the oldest members of the Duodecim, the 12 families that formed NOL. They put such an emphasis on preserving their magical abilities that when children who exhibited weaker ars magus aptitude started being born, members resorted to incest and inbreeding in the mad delusion they would get stronger, much to the disgust of the other families. It's specifically noted that Tsubaki isn't the firstborn child of her parents, she's merely the first to survive.
  • Crusader Kings:
    • Crusader Kings II:
      • Some of the best character traits in the game are hereditary, and become more likely the more common they are in a newborn character's ancestry. The game's mechanics forbid marriage to a sibling, child, or parent, but allow grandparent-to-grandchild marriages, among other icky things. Inbreeding excessively will lead to the dreaded "Inbred" trait, which gives a negative 5 to all stats on top of making a character ugly as sin, disgusted by everyone, and unlikely to breed further.
      • All of this is thrown off the window with Zoroastrians, for whom incestuous marriages are holy, and increase their popularity with vassals. To help keep Zoroastrian families from descending into deformed messes, the game lets their rulers keep three concubines for non-inbred — but legitimate — children. The general "divine blood" modifier that handles making incestuous marriages holy also behind-the-scenes significantly decreases the risk of getting the (very negative) inbred trait from being inbred... while increasing the risk of getting the lunatic trait from being inbred. This mechanic is inspired by the practice of xwedodah, mentioned in the Real Life section below.
      • The Messalian heresy also allows for incest, but no concubines.
      • Mentioned in the "Lust" live-action trailer.
        King: But the earl is my uncle, that would make her my... half-sister?
        Adviser: It's the other one, sir, she's your cousin.
    • Both Zoroastrianism band Messalianism came back in Crusader Kings III, and not only that it's possible to create your own religion that allows incest. The game also introduces non-incestuous variants of Zoroastrianism if you wish to avoid this. And the "Blood" dynasty trait improves the chances of a dynasty producing heirs with good genetic traits and reduces the chance of inheriting bad ones (such as the ones leading to Inbred), which is quite helpful for a dynasty engaging in repeated eugenic incest.
  • The Black-Briars of The Elder Scrolls V: Skyrim are not royalty, but are still arguably the most powerful family in Skyrim, and this seems to be implied by dialogue from the Eldest son, Hemming. There are certain instances where Hemming will refer to Sibbi and Inguin, his siblings, as his children. Likewise, they are tagged as his children in the game's files, with Maven, the family matriarch, as their grandmother. Yet Sibbi and Inguin will also refer to Maven as their mother. Even worse, Hemming can occasionally be found sleeping in Maven's bed, with his mother. The above may simply be the result of an earlier concept of the family in which Hemming and Maven were married, that remained partially in the game's files. Though for a character to go from another character's spouse to their offspring is rather unusual on its own...
  • Fire Emblem: Genealogy of the Holy War is infamous for this. In the first half of the story, most of the player characters are from noble houses, and the player can choose to pair up two sets of cousins (one was implied to be a case of Brother–Sister Incest before later supplements stated them to be distant cousins). The Big Bad's plan also hinges on having two half-siblings bear a child. This is because of an ancient Blood Pact made centuries ago between humans and dragons, and carriers of "major" Holy Blood can be created from a union of two "minor" carriers. Depending on who married who in the first-gen, there are also a number of possibilities for Kissing Cousins in the next generation.
  • In Fire Emblem: Three Houses, Edelgard and Constance's supports heavily imply that House Nuvelle frequently married their relatives in order to keep fewer people from learning about their Crest of Noa. Unfortunately, this backfired on them during the Dagda-Brigid War, as it left them with fewer allies to come to their aid, resulting in everyone but Constance getting wiped out.
  • In Kult: Heretic Kingdoms, the Heroic Lineage of the person who killed god is not precisely "royal", but because it carries power over the magical sword he used, people have tried to control the bloodline in similar ways. Taryn Arkor, a descendant, is referred to as inbred, and his own practices (using his fellow descendants as breeding stock for sacrifices) wouldn't have left the gene pool any more diverse.
  • The Winchester Family from The Sims 3 Midnight Hollow neighborhood are an allusion to this. Although the brother and sister (who live alone together) cannot be romantically involved with one another; their identical physical characteristics, personality traits, and backstory, make it obvious that this was not an uncommon practice in their family.
  • Implied with the von Auslese dynasty of Liberl in the Trails in the Sky trilogy. At one point in the second game, a family member is compared via a genetic scanner to the Founder of the Kingdom Celeste D. Auslese (who had lived twelve centuries previous, making the genetic separation roughly 40 generations), and surprised by how high a percentage their genetic match is (73%, suggesting that roughly three-quarters of Kloe's ancestors could trace their lineage back to Celeste).
  • The Nanayas in Tsukihime often encourage this to preserve their innate "anything-killer" ability.
  • In WildStar the Luminai, rulers of the Dominion, are Eldan/Cassian hybrids of at least 50% Eldan blood. Maintained by a law barring Luminai from breeding with Cassians. Though Highborn Cassians, the next step down in the caste system, have some Eldan blood and act just as aristocratic.

  • According to Word of God, most of the more elite Orphic families in the world of Blindsprings were somewhat inbred because Orphic powers are inherited. It's implied this might have been part of the reason the Llyn family was having trouble producing the next generation by the time they were overthrown, and possibly the reason the conspicuously-red-headed-in-a-family-of-brunettes protagonist Tamaura was born out of wedlock, with hints that her conception was deliberate either on the part of her mother or the spirits. As a result, most Orphics are related to each other, and Imogen and the other Thorne sisters are actually Tammy's very distant relatives.
  • In Inverloch, only humans who have elven ancestry can use magic, and the races are so insular that there is only one known half-elf after centuries. The human city of Aydensfell is the only one where mages live and congregate... and the vast majority of them are redheads. Despite Lei'ella dismissing it as a rumor, the implication is clear.
  • Stolen Bride: Obril is so incestual, they're openly proud of it; their current goal is to make the king and queen siblings. Naturally, this has screwed up their genetics so thoroughly that the queen had ten miscarriages before she died from the strain, the crown prince is a dangerous narcissist, and the second in line is a manipulative sociopath due to his inability to feel pain.

    Web Original 
  • RWBY Recaps uses this as the comedic quirk of Blake's parents- they're first cousins, as is traditional for royalty, and they're kind of ditzy due to the inbreeding. Matt notes that there really isn't much else to make fun of, since Blake's parents are just straight-up Good Parents.
  • SCP Foundation: SCP-3288 is a branch of the Hapsburg family that took this to severe extremes: thanks to Leopold I experimenting with alchemy, the family is able to interbreed with few of the downsides of inbreeding. The deformed ones are sent to underground crypts, but otherwise don't suffer any ill effects such as poor health and infertility: in fact, their deformities make them stronger. As time passed those in the underground kept breeding with each other (with parental and sibling incest being commonplace) until their blood got so 'pure' and toxic that even children conceived with a non-Hapsburg woman (usually through rape) will come out pure Hapsburg (and in this context, 'come out' means they eat their way out of their mother). The Hapsburg they captured revealed that this was their entire plan, and they won't stop until the entire earth is populated by Hapsburgs. The worst part? The Foundation's only contained some crypts. They don't know how many are actually out there.

    Western Animation 
  • Farzar: Queen Flammy of The Zygloot System comes from a long line of royal inbreds, who are all a bunch of hideously disfigured mutants with comically exaggerated deformities that are Played for Laughs. The royal family resents her for marrying outside the family, and tainting their gene pool with Renzo's foreign DNA and producing a normal-looking child with naturally functioning body parts. The most prominent family member is Flammy's twin brother/cousin, Splammy, who was the intended husband for Flammy before she broke royal tradition. Splammy now serves as an abhorrent admirer to Flammy and still chases his sister's tail in hopes she'll divorce Renzo and remarry him.
    Flammy: Splammy! You're here? I didn't think you'd come.
    Splammy: Of course, I came. You made me come ... but enough about our 7th birthday.
  • Tigtone: The king and queen of Propecia are twins. What is even more disturbing is that they are also conjoined twins, who do have sex with each other, somehow. The fact that their son is a normal-looking human who doesn't look too much like them turns out to be foreshadowing that he was born from the queen having an affair, somehow. It is later confirmed that the prince is actually the son of the queen and the court wizard. It is unknown how the queen had this affair without the king knowing about it and it's probably for the best.
  • The Loud House Movie: The present-day Loud family is completely identical to their distant ancestors from 400 years ago, which possibly raises questions about incest.

    Real Life 
  • Many Ancient Egyptian Pharaohs married their cousins or in some cases siblings (especially half-siblings). King Tut suffered from any number of possible genetic disorders from being the offspring of a brother and sister. Contrary-wise the 12th Dynasty (19th-18th centuries BC), one of the most successful in Egypt's long history, married brother to sister for seven or eight generations without noticeable ill effect. It was once believed that incestuous marriages were common among other families and commoners, but it's now thought that using "my brother" and "my sister" between married couples could also have been the equivalent of "dear" or "darling" and not literal (as they were common terms of affection in wider society—friends and even business associates are regularly recorded as calling each other "brother"/"sister").
  • When the Macedonian Ptolemies took control of Egypt after the split-up of the empire of Alexander the Great in the 4th century BC, they revived the Egyptian practice of wedding brothers to sisters to enamor themselves to the Egyptian people, and consequently to keep the Ptolemaic dynasty relatively free of Egyptian riff-raff. They also revived the Egyptian practice of brother-sister spouses ruling jointly, meaning neither party officially had more power than the other. This led to the succession battle that eventually placed the famous Cleopatra VII as the sole ruler of Egypt despite being a woman.
  • The practice of xwedodah, marriage of close family members to each other, in the noble families of Persia prior to the Arab invasion. Very little information about this practice has survived into the modern day (and it is not practiced by modern-day Zoroastrians), but it appears to have been a practice grounded partially in religion and partially in culture and was most likely restricted to royals and priests.
  • Like their counterparts in Egypt, ancient Celtic nobility in Ireland and Britain were known to engage in brother-sister relations, possibly for religious reasons.
  • In the Kingdom of Hawaii and its predecessors, intentional incestuous mating was encouraged amongst the ruling classes, despite incest being very rare in other Polynesian cultures. This was because the Hawaiians believed marriages between blood relatives would produce children with very high mana levels, which would translate into semi-divine status that granted mental and physical superiority. Extensive genealogies were kept in order to produce the most inbred (and thus, godly) chiefs possible. The commoners were forbidden to do this out of fear that they would start producing children with chieflike levels of mana.
  • The ancient Korean kingdom of Silla (first millennium CE) had a strict bone rank system that determined one's social class. And only Sacred Bone, royal dynasty, could ascend to the throne. However, to be born as a Sacred Bone, one must have both Sacred Bone parents, which resulted in the royals marrying within the family. This bone rank system was so strict that when there were no more male Sacred Bones, the female Sacred Bones ascended to the throne, despite there being other males with royal blood. Marrying one's half-siblings was socially accepted and often happened, not only among royals but also among nobles.
    • Also, in the Goryeo Kingdom, the Silla Kingdom's successor, the royal dynasty (The House of Wang) still married within the family, especially princesses, as all of them, without exception, married within the family for the reason to protect the Kingdom's dynasty. Since Goryeo acknowledged women's right of inheritance, princesses' male descendants of different clans (their fathers' clans) could have claims to the throne through their mothers. Therefore, to prevent this from happening, Goryeo princesses all married within the family to maintain the royal lineage. When they married, they were given either their mother's or grandmother's surname, so to lessen the feeling of discomfort.
    • King Mokjong of Goryeo. His parents were cousins. His paternal grandparents were half-siblings. His maternal grandparents were half-siblings. Both sets of grandparents were each other's half-siblings. Mokjong had only one great-grandfather. Normal people have four.
  • In ancient and feudal Japan, it was common for noble and imperial families to arrange marriages between half- and (more rarely) full-siblings, cousins and even aunts/uncles and nephews/nieces because The Patriarch of these families tended to have boatloads of children from many different women, and this was a convenient way of tidying up familial loose ends and folding branches of the family back into the main House. In particular, it was rather common for the reigning emperor to be married to a close relative of his ruling shogun. Since the latter tended to also form dynasties, this meant that the two family trees often intertwined. This is, however, subverted in terms of biology as children of (unrelated) royal concubines are simply declared to be legitimate children of the Emperor and his cousin-wife.
  • In traditional Arab society, it is customary for cousins to marry — although often more as a last resort for a woman who has been unmarried for too long than as a first choice (such women get told, "There's always your cousin"). However, among aristocratic families, the desire to keep family fortunes together influences this — under Islamic inheritance law, daughters are entitled to inherit (only half of what their brothers inherit, but still), and heirs cannot be disinherited except in extreme circumstances, so cousin marriage keeps the family fortune in the family.
  • Claudius made an edict declaring that an uncle marrying his niece didn't count as incest so that he could marry his own niece Agrippina, mother of Nero (by her previous husband, a cousin).
  • Eighth-century Irish Princess and Roman Catholic saint Dymphna's mother passed away, and her father decided to marry her. She fled with a few companions, but when the charitable work in Belgium she was doing caught her father's attention, she and her friends were ultimately martyred, and the city whose mental health facility she started is one of the most envied, studied, and effective to this day.
  • The House of Habsburg (originally from a part of the globe that would, interestingly enough, evolve into direct democracy Switzerland), which ruled large parts of Europe for several hundred years (with branches in Austria, Hungary, Spain, Portugal, and parts of Italy), was notorious for this: they acquired a lot of land through dynastic marriages and tried to avoid having the same thing happen to them by keeping things in house. The last of the Spanish Habsburgs, the infamous Charles II of Spain, was actually more genetically inbred than a "typical" product of Brother–Sister Incest would have been thanks to generations of cousin/cousin and uncle/niece marriages. His health problems were so severe that even the royal portrait artists — who were being paid to make him look good — couldn't hide his very prominent lower jaw and strangely squashed nose. He has been described as "short, lame, epileptic, senile and completely bald before 35, always on the verge of death but repeatedly baffling Christendom by continuing to live."note 
    • To put this into context, Philip III was Charles II's grandfather through his father and his great-grandfather through his mother. Philip III was related to his own wife, Margaret of Austria, in at least 6 ways (first cousins once removed, 2nd cousins through two different branches, 2nd cousins once removed through two different branches, and 3rd cousins) which made his relationship worse than a "typical" first cousin pairing. This came about because Margaret was the result of an uncle/niece pairing while Philip III was a product of an uncle/niece (also 1st cousins once removed) pairing. Charles II's other great-grandfather was Holy Roman Emperor Ferdinand II. Ferdinand II was related to his own wife, Maria Anna of Bavaria, in at least 3 ways (1st cousins, 2nd cousins once removed, and 3rd cousins). Despite Philip III and Margaret not being true 1st cousins, they were actually more closely related to each other than Ferdinand II was to Maria Anna. Philip III's daughter, Maria Anna of Spain, and Ferdinand II's son, Holy Roman Emperor Ferdinand III, married each other (adding yet another 1st cousin connection into the mix). Philip III's son, Philip IV, then married the product of that incest, Mariana of Austria, to add one last uncle/niece pairing into the mix. To get a good reference, it's scientifically recommended that you not are more closely related to your spouse than 3rd cousins to avoid most complications from incest. An uncle/niece pairing is already 32 times closer to each other than 3rd cousins are.note 
    • Archduchess Maria Antonia of Austria had an inbreeding coefficient of 0.3053 (for comparison, a child from Brother–Sister Incest or Parental Incest has a coefficient of 0.25 and Charles II had an inbreeding coefficient of 0.254) due to her parents and grandparents being uncle and niece. Surprisingly, she was relatively healthy and lived to adulthood.
  • Queen Victoria married her first cousin Prince Albert (his father and Victoria's mother were siblings) and their nine children were married into so many other European royal houses. Queen Victoria was also a carrier for hemophilia through an apparent random mutation, and the result was that most of the European royal families were hemophiliacs and carriers into the 20th century.
    • This had a particularly strong effect in Tsarist Russia: Tsar Nicholas II's son Alexei inherited the gene for hemophilia that Victoria carried because his mother, Tsarina Alexandra (born Princess Alix of Hesse and by Rhine), was one of her grandchildren through her daughter Princess Alice. Alexei's illness heavily influenced the Imperial couple's decisionmaking, and not for the better—it led them to trust Grigori Rasputin, which lost them support among key members of the aristocracy who would later turn their backs on Nicholas and Alexandra in February 1917.note 
    • When the post-Communist Russian government wanted to verify that the human remains found in Siberia were those of the late Tsar Nicholas, they needed a close relative to match the DNA. Prince Philip, Duke of Edinburgh (descended from Victoria through Princess Alice, whose daughter Alix married Tsar Nicholas, and directly related to Nicholas through common descent from Nicholas's maternal grandfather Christian IX of Denmarknote ) was tactfully approached to give DNA samples. Philip's DNA proved the Romanoff DNA beyond all possible doubt.
  • Chulalongkorn, the famed modernizing reformer king of Siam (now Thailand), had four wives, all of whom were half-sisters of his.
  • The House of Hashim:
    • There was the Double In-Law Marriage between Abdullah I of Jordan to Musbah bint Nasser, and Abdullah's brother Faisal I of Iraq to Musbah's twin sister, Huzaima. Musbah and Huzaima were first cousins to Abdullah and Faisal, all four having the same ancestor as their paternal grandfather Ali bin Muhammad. Abdullah's son Talal, in turn, married Zein al-Sharaf, Musbah's and Huzaima's niece and thus his second cousin. And Talal's son Hussein (father of current King Abdullah II) continued the tradition by marrying Dina bint Abdul-Hamid, his third cousin once removed (she's a great-granddaughter of Awn ar-Rafiq, brother of the aforementioned Ali bin Muhammad), although she only gave birth to a daughter before divorcing Hussein, and his heir Abdullah II was conceived through his English second wife, Antoinette Gardiner.
    • Meanwhile, Faisal I's son, Ghazi, married his first cousin Aliya. This enabled her family, the Hejazi branch of the Hashemites, to seek refuge in Iraq after they were deposed by the House of Saud, and Aliya's brother, 'Abd al-Ilah, subsequently became regent and Crown Prince of Ghazi's young son Faisal II (who was simultaneously his nephew and first cousin once removed). Unfortunately, Iraq violently abolished its monarchy a couple of decades later, killing 'Abd al-Ilah and most of his relatives (only a sister survived).
  • Vittorio Emanuele III of Italy was infamously short and of poor health thanks to generations of cousin marriages among his ancestors finally catching up to his dynasty. He was perfectly aware of this to the point that as the heir to the throne, he torpedoed his possible engagement to a German princess precisely because they were related... Resulting in literally all royals of Europe joining forces to ensure he'd marry Elena of Montenegro, to whom he wasn't related. His son Umberto II was much taller and in better health.