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Double In-Law Marriage

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A marries C. B marries D.

Atticus: Double first cousin.
Scout: How can that be?
Atticus: Two sisters married two brothers.

Alice and Bob are siblings. So are Charlie and Dana. Alice marries Charlie, while Bob falls in love with Dana. The gender configurations can vary — it could be two sisters who each marry one of a pair of brothers, or any variation including Queer Romance. In other words, it's any time one pair of siblings marry another pair of siblings. Someone marries the sibling of their own sibling's spouse.

A quick way to achieve Weddings for Everyone. Or if the weddings don't take place at roughly the same time, the first wedding provided the ideal opportunity for the second couple to get to know each other. Another variant, popular in the Romance Novel, is that the first couple dies, leaving a child, and the second couple meet, argue, and finally marry because of their dispute over custody.

This can lead to a major Tangled Family Tree as the children of one couple are "double cousins" to the children of the other. Since they are as genetically twice as similar as most cousins, Kissing Cousins is even more discouraged in such cases. This gets ramped up in cases where identical twins are involved, in which case the cousins are biologically as close as half-siblings (with one set) or full siblings (with two sets). Can also overlap with Retroactive Stepsibling Relationship.

A popular way to resolve a Sibling Triangle. Compare Best Friends-in-Law, which only involves three people. Not to be confused with Settle for Sibling, although overlap is certainly not impossible. Not at all the same as Brother–Sister Incest, where someone marries their own sibling.


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    Anime & Manga 

  • In the Child Ballad Rose the Red and White Lily, a pair of sisters and a pair of brothers — their stepbrothers — fall in love. It ends with the king ordering the two couples to marry.

    Comic Books 
  • The tie-in comic for Batman Beyond revealed that King and Queen each had a twin and also got married and their daughter resembled King and Queen's.
  • Disney Ducks Comic Universe: Don Rosa once stated in an interview that he sees Mr. Duck (Huey, Dewey and Louie's father) as Daisy's brother, and that Daisy is really the boys' aunt. Their mother, Della Duck, is Donald's sister. Donald and Daisy are, of course, dating. The canonicity of this statement is dubious, however.
  • This occurs in Jem and the Holograms (IDW) with dating, not marriage. Kimber is dating Stormer. Stormer is the sister of Craig, who happens to be dating Kimber's foster sister Aja. Craig finds it amusing. They go on a double date, however Craig and Aja end up finding their siblings to be Sickening Sweethearts.
  • Spider-Man: This is sometimes the origin for Peter Parker's Aunt May and Uncle Ben's relationship with his parents. Originally, Uncle Ben was just Richard Parker's considerably older brother, and Aunt May and Mary Fitzpatrick-Parker were unrelated, but some recent versions have the women as sisters as well.
    • This is specifically hinted at in Ultimate Spider-Man, where Aunt May refers to her sister's death and calls Peter her sister's responsibility during a fight.
    • In the regular continuity, however, it's often noted that this is not the case, and Aunt May (Reilly, not Fitzpatrick) and Peter Parker are not related by blood at all, making her selfless love and doting nature all the sweeter.

    Fairy Tales 
  • In the oldest variant of Beauty and the Beast, Beauty and the Beast are Kissing Cousins from such an arrangement, between two royal brothers and two fairy sisters.
  • In the original Brother and Sister, the sister is married to the king at the end while the brother is still single (but fortunately no longer a deer). Some versions give the king a sister for him to hook up with.
  • In the Sicilian fairy tale Cacciaturino, a widowed king and a widowed queen, and at the same time, her seven sons marry his seven daughters, for an eight-fold marriage.
  • In the Arab fairy tale, The Father of Seven Sons, the father takes it into his head that his sons must marry seven sisters. He does find such brides for them.
    • Other Arab fairy tales reflect the tradition of Kissing Cousins; a woman falls in love with a man and that's a problem because she's betrothed to her first cousin. If he's willing to give her up, this is often amicably resolved by the new bridegroom offering the cousin a bride who is his cousin.
  • In Asbjørnsen and Moe's The Giant Who Had No Heart in His Body, there's a six-fold in-law marriage: six brothers marry six sisters, with only the youngest brother marrying a different bride.
  • In Joseph Jacobs's Kate Crackernuts, Kate, having rescued the sick prince, finds that her stepsister Anne and the prince's brother had fallen in love at first sight.
  • In Madame d'Aulnoy's Princess Belle-Etoile link, a king and his brother marry two sisters. Unfortunately, there is a third sister, and the king and his brother don't have a third brother for her. She marries an admiral instead and becomes jealous. (Their children, three of the king's and one of the brother's, are then abandoned together, and despite being raised as brothers and sister, the king's daughter and the brother's son manage to fall in love and end up married.)
  • In The Brothers Grimm tale Snow-White and Rose-Red, Snow White winds up with the prince who was turned into a bear while Rose Red marries his brother. Since the girls grew up sharing everything, this is the closest they can come to sharing a husband, too. In the Grimm's Fairy Tale Classics adaptation, there's a bit of Adaptation Expansion: the brother appears earlier in the story, Rose Red helps him when he's wounded and there's quite a bit of Ship Tease between the two.
  • In an Indian fairy tale/riddle, a prince and a king find the tracks of a queen and a princess who are escaping the armies that overwhelmed their kingdom. The prince assumes that the smaller footprint is the princess and tells the king that he should marry the woman with the larger footprint, he'll marry the woman with the smaller. Then they find the queen and princess and learn that actually the queen has the smaller foot. So they marry as they agreed: the prince and the queen, and the king and the princess. The riddle is: since both unions had children, what relationship were the children to each other?

    Fan Works 

    Film — Animation 
  • A Goofy Movie: The "After Today" musical number scene features twin boys kissing twin girls.
  • The Book of Life: Sisters La Muerte and La Noche are married respectively to Xibalba and his brother El Camuco. Taken a step further with Word of God confirming Big Bad of Maya and the Three, Lord Mictlan is a brother of Xibalba and El Camuco and his wife, Lady Micte, is sister of La Muerte and La Noche.
  • The plot of Mulan II starts when the Emperor has Mulan escort his three daughters to a neighboring kingdom to marry its ruler's three sons, as part of an alliance.

    Film — Live-Action 
  • The Birth of a Nation ends with Phil Stoneman, his wife Margaret, her brother Ben Cameron, and his wife Elsie, who happens to be Phil's sister, on a double honeymoon.
  • At the end of The Legend of Frenchie King, the Leroi sisters (minus Louise) marry the Sarrazin brothers, resulting in a quadruple in-law marriage.
  • The Hallmark Made-for-TV movie A Princess for Christmas has this with a slight twist: a woman is Promoted to Parent after her sister and her husband die, then falls for her dead brother-in-law's younger brother, whom she'd never met before.
  • In Tumbleweed, Sarah Blandon is very keen for her sister Laura to marry her husband's brother Lam. Laura is notably less keen on the idea.
  • Twice Two (1933) begins with Laurel and Hardy married to each other's sister. As played by both actors in drag.
  • Twins (1988) ends with the eponymous twins marrying twins and each having twins of their own.

  • Used in Ada, or Ardor to set up the incestuous cousins, although they later turn out to be siblings as both were the product of an affair between the double in-laws.
  • Lily and Daisy Calloway (sisters) married Loren Hale and Ryke Meadows (half-brothers) in Addicted.
  • From the Anne of Green Gables series:
    • In Anne's House of Dreams, Leslie's husband Dick had a "double cousin" named George who looked almost like his twin. When the brain-damaged man everyone had assumed was Dick for thirteen years was cured, it turned out to be George.
    • Rilla of Ingleside has Anne's children Jem and Nan both marry into the Meredith family.
  • There exists somewhere an "ending" written for the Arabian Nights that was made several hundred years later, in which Shahryar had magically fallen deeply in love with Scheherazade, decided to keep her, and then his brother magically fell in love with her sister so they could be one big happy family.
  • Ascendance of a Bookworm: The Ehrenfest and Frenbeltag archducal couples are in such a marriage. Ehrenfest's archduke's wife is the younger sister of Frenbeltag's archduke, whose wife is the older sister of Ehrenfest's archduke. Ehrenfest being led by the younger siblings all while having been less damaged than Frenbeltag by a recent civil war results in its leaders having trouble saying "no" to requests for help from Frenbeltag.
  • In The Bacta War, we learn that Lanal Darklighter is Gavin's aunt on both sides of the family because she is both his mother's sister and his paternal uncle's wife.
  • In Amy Tan's The Bonesetter's Daughter, sisters Lu Ling and Gao Ling marry brothers Edwin and Edmund Young.
  • A Brother's Price has this trope seen as very positive since it means closer bonds between families and makes cousins more like sisters. When Cullen is married to the older Whistler sisters, he hopes to get their cousin married to his sisters.
  • A minor side-plot in Tom Clancy's Clear and Present Danger concerns a pair of criminal twin brothers who fell for a pair of twin sister hookers, and got sent to prison for murdering their pimp. They wind up getting out again after a little unofficial deal is struck with the police, killing a pair of Cartel Goons who were set to get off on a technicality, inside the prison. As far as we know, the two sets of twins all lived happily ever after while the main plot moved on.
  • In Jacqueline Wilson's Double Act, Garnet has always assumed she and her twin sister Ruby would marry a pair of twin boys.
  • In the Double Trouble and Triple Trouble series by Michael J. Pellowski, this is the explanation given for why the Daniels twins have an identical cousin. Their father's older brother married their mother's younger sister.
  • Emma: Brothers John and George Knightley marry sisters Isabella and Emma Woodhouse. As in Sense and Sensibility, the heroine's marriage takes place at the end, while her sibling's marriage took place before the start of the book, so Emma and her Mr. Knightley have been Like Brother and Sister all her life.
  • In Malevil, Emmanuel's father and uncle married a pair of sisters.
  • Book 4 of The Faerie Queene: Brother and sister Campbell and Canacee married sister and brother Cambina and Triamond.
  • In Alethea Kontis's Enchanted, a pair of sisters marry, not a pair of brothers, but a father and son, so they are stepmother-in-law and stepdaughter-in-law.
  • This would have happened in Gone with the Wind if brother and sister Charles and Melanie Hamilton had married their cousins Honey and Ashley Wilkes, respectively, as had long been planned, in keeping with the family tradition of the Wilkes and Hamilton clans intermarrying. However, Scarlett O'Hara decided to interfere, and in a failed attempt at getting Ashley for herself or at least making him jealous, she ended up married to Charles.
  • In Orson Scott Card's Homecoming Saga, brothers Nafai and Issib marry sisters Luet and Hushidh.
  • In the High Valley by Susan Coolidge: Lionel and Imogen Young marry Joanna and Dorry Carr. Lionel describes it as 'change partners all round and down the middle'
  • First Lensman Virgil Samms and his cousin George Olmstead are (allegedly) remarkably similar in appearance because of a two-generation stack of this phenomenon. Supposedly, "quadruple first cousins" is the closest the genealogists could come to computing what had actually happened. (Notably, their parents were not only a pair of brothers and a pair of sisters ... they're a pair of identical twin brothers and a similar pair of sisters who ALSO happen to be first cousins with each other.)
  • Mansfield Park: Mrs. Grant plans for her brother and sister Henry and Mary Crawford to marry siblings Julia and Tom Bertram. They both blow it, starting by flirting with the other two Bertrams Maria and Edmund. Note to Shippers On Deck: Make sure the sides are balanced before attempting this trope. Ironically, at least 2 Fan SequelsSusan Price and Mansfield Revisited — invoke this trope by marrying Fanny's sister Susan Price to Edmund's brother Tom Bertram
  • Northanger Abbey: John and Isabella Thorpe plan to marry Catherine and James Moreland, respectively, but ultimately don't because John is a pompous windbag and Isabella is an incurable flirt.
  • In Once Upon a Marigold, two of Princess Marigold's older sisters are married to the twin princes of Zandelphia. This becomes triple in the end when Marigold marries Christian, revealed to be the twins' long-lost brother and thus the true heir to throne of Zandelphia.
  • In Emily Rodda's Pigs Might Fly, this happened to Enid and her sister, who met their future husbands (brothers) at the same party. This is justified as it happened during a UEF (Unlikely Events Factor) Storm, which causes unlikely events such as pigs flying.
  • In the Ramsey/Brady collection of Harlequin Romance novels, four Brady sisters end up married to the four Ramsey brothers. For added bonus, the oldest sister marries the oldest brother, etc. With only four Ramsey brothers, poor fifth and youngest sister Colleen has to find an entirely different guy on her own.
  • In the Safehold Zhan and Zhanayt (Cayleb's younger siblings) end up marrying Nahrmahn and Mahrya (the children of Nahrmahn Sr). The betrothal of Zhan and Mahrya was an Arranged Marriage (which became a Perfectly Arranged Marriage) to tie Emerald into the Charisian Empire while the marriage of Nahrmahn and Zhanayt was a case of them falling in love.
  • Sense and Sensibility: John Dashwood and his half-sister Elinor Dashwood marry sister and brother Fanny and Edward Ferrars. John and Fanny are already married before the book begins, but Elinor and Edward don't get married until the end (Edward's Arranged Marriage and Childhood Marriage Promise to Lucy were in the way).
  • In Shanghai Girls by Lisa See, sisters Pearl and May marry brothers Sam and Vern Louie, and Pearl has a daughter. Subverted because Sam is not really Vern's brother, he was adopted by the Louie family so he could get to America, and Pearl's daughter is really May's daughter with another man.
  • A Song of Ice and Fire:
    • At the very beginning, best friends King Robert and Ned Stark intend to do this. They had already betrothed Sansa and Joffrey, while Robb and Arya escorted Myrcella and Tommen to dinner, with the implication that they were trying to set them up.
    • Catelyn Stark makes a contract with Walder Frey for Robb and Arya to marry two Frey siblings.
    • According to The World of Ice & Fire, siblings Daeron II and Daenerys Targaryen (Queen Daenerys' namesake) were wedded to a pair of siblings from House Martell: Myriah and Maron, respectively.
    • Jacaerys and Lucerys Velaryon, sons of Rhaenyra Targaryen, were betrothed to Baela and Rhaena Targaryen, daughters of Rhaenyra's second husband, Daemon. However, both boys died during the Dance of the Dragons, and Baela and Rhaena ended up marrying different people after the war.
  • Mentioned in an aside in To Kill a Mockingbird, although not actually featured. Atticus mentions the concept of double cousins, saying "two brothers married two sisters." The pair of young friends Scout and Dill work on figuring it out, and reason that if Dill had a sister whom he married, and Scout and her brother got married, their kids would be double cousins. Only off by a little bit there...
  • Tolkien's Legendarium: This shows up several times in The Silmarillion and The Lord of the Rings.
    • Sam's sister Marigold Gamgee married Rose's brother Tolman Cotton.
    • Galdor, heir to the house of Hador, and his sister Gloredhel marry Hareth of the Haladin and her brother Haldir.
    • Galdor and Hareth's sons Húrin and Huor marry first cousins Morwen and Rían.
    • Siblings Éomer and Éowyn of Rohan marry first cousins Lothíriel of Dol Amroth and Faramir of Gondor.
    • Bilbo's father (Bungo Baggins) and his first cousin Rosa married siblings Belladonna and Hildigrim Took. (Bilbo's and Frodo's fathers were first cousins once removed, and their mothers were aunt and niece—look through the family trees at the end of The Lord of the Rings and you can find endless cases of people marrying their in-laws as well as Kissing Cousins.)
  • Although it's only part of the act that they keep up to appear human, the Cullen/Hale "kids" appear as this to outsiders in the novel Twilight. Alice Cullen is with Jasper Hale while her "brother" Emmett Cullen is with Jasper's "sister" Rosalie Hale. It's implied that the family puts on some variety of this trope whenever they all move to a new location together and that Bella and Edward will be folded into the deception now that they're together and both vampires.

    Live-Action TV 
  • Gilmore Girls had one episode where the Inn hosted a double wedding between two sets of twins.
  • Played with on Los Hombres de Paco. Paco and Pepa are brother and sister and Silvia and Lola are sisters. Paco and Lola were married but got divorced before Pepa and Silvia got married later on in the series.
  • Howe And Howe Tech is about a company run by identical twin brothers Mike and Geoff, with their wives, Tammy and Tracy, handling office work. Tammy and Tracy are sisters.
  • Into the West used this in the first episode.
  • Played for Laughs in The Late Show with Stephen Colbert when Stephen finds out that, due to copyright, he is unable to use his character from The Colbert Report. To get around this, he introduces the character's identical twin cousin (their parents were two sets of identical twins and they were conceived at the same time).
  • The Legend of Xiao Chuo has a complicated version. All three of the Xiao sisters marry men from the Yelü family: Yan Yan marries Xian, Wuguli marries Xian's cousin Xi Yin, and Hu Nian marries Xian's uncle Yansage.
  • Liv and Maddie: Artie wishes for this, with him dating Liv and his brother Diggie dating Liv's twin sister Maddie. Unfortunately, Maddie and Diggie break up and Liv has no interest in Artie and considers him an Abhorrent Admirer.
  • In Lost in Austen, after Mr. Collins marries Jane, he tries to marry his brothers off to the younger Bennet sisters. It doesn't quite work out.
  • Married... with Children: In "How to Marry a Moron", Kelly is engaged to a rich guy named Lonnie Tot and Lonnie's ugly sister is interested in Bud. When Lonnie's dad says he'll make Al his business partner if both marriages take place, Al eagerly announces Bud's engagement.
  • Nirvana in Fire:
    • A really strange example in that Jingrui is adopted by both the Xies and the Zhuos so they are in a sense in-laws through him. Then his little sister (from the Xies) and his older brother (from the Zhuos) get married so they are double-in-laws. Jingrui laughingly notes that when his sister has her baby he'll be both a paternal and maternal uncle.
    • Grand Princess Jinyan married Lin Xie while Jinyan's brother the Emperor married Lin Xie's sister Lin Yueyao; this causes Prince Qi and Lin Shu to be "double cousins". Because Consort Jing is Lin Xie's adopted sister, Prince Jing and Lin Shu are also considered "double cousins". This goes a long way in contributing to Everyone Is Related.
  • Pasión de gavilanes: The popular telenovela features a triple-in-law situation, as the plot concerns the entanglements between the Reyes and Elizondo families. Over the course of the series, the three Reyes brothers fall for a different Elizondo sister.
  • Queen for Seven Days has an especially bizarre example since the wives are actually aunt and niece, but are close enough in age to be sisters. Lee Yung marries Shin Bi, and later his half-brother Lee Yeok marries Shin Bi's niece Chae-gyeong.
  • Roseanne: Darlene and Becky Conner married David and Mark Healy, respectively.
    • Or the other way around, according to the finale.
    • The characters had a lot of fun joking about David and Darlene's relationship after they essentially adopted him as a member of the family long before Becky got married. It's to the point that, when Darlene and David get engaged, Roseanne celebrates the fact that they are officially the most redneck white trash in town.
  • In Weeds, Nancy Botwin's sister hooked up temporarily with Uncle Andy, who was the brother of Nancy's dead husband.
  • The White Queen: As in Real Life, two York brothers, George of Clarence and Richard of Gloucester, are married to the two Neville sisters, Isabel and Anne, respectively.
  • Whodunnit? (UK): In "A Piece of Cake", Betty Anderson is married to James. Her sister Marjorie Tempest is engaged to James' older brother, Captain Alexander Anderson, who becomes the Body of the Week.

  • Natsuki Enomoto and Yuu Setoguchi are the first pair to become an Official Couple in the Confession Executive Committee ~Love Series~ , eventually getting married later down the line. Meanwhile, Natsuki's little brother Kotaro is in love with Yuu's younger sister, Hina. Although Hina initially had a crush on her upperclassman Koyuki, she eventually reciprocates Kotaro's love after Koyuki graduates. Later songs imply that Hina and Kotaro remained together throughout Natsuki and Yuu's engagement.

    Myths & Religion 
  • A rabbinic legend says that The Bible's Laban intended to marry his two daughters to their two male cousins—the older two, Leah and Esau, would be one couple and Jacob and Rachel would be the other. Averted because Leah prayed to God that she wouldn't have to marry the wicked Esau, and He arranged for both sisters to marry Jacob instead.
  • According to Josephus, Levi and Issachar married two sisters named Adinah and Aridah, while their brothers Gad and Naphtali married sisters named Merimit and Uzit.
  • In Classical Mythology there were the Danaids, fifty sisters, who were in a mass Arranged Marriage to their fifty male cousins. They are eventually compelled to go through with the marriages, and then all but one of the sisters murder their husbands in their sleep.
  • In Greek Classical Mythology, brothers Menelaus and Agamemnon married half-twin-sisters (different fathers, don't ask) Helen and Clytemnestra, respectively.
  • For that matters, Helen and Clytemnestra's brothers, Castor and Pollux abducted and married Hilaeira and Phoebe, daughters of Leucippus who themselves were betrothed to another pair of brothers Lynceus and Idas. It didn't end well, Lynceus and Idas killed Castor to avenge their honor.
  • Arthurian Legend:
    • In most versions of Gareth's story, after he marries his Damsel in Distress Lyonesse, her sister, the Damsel Errant Lynette, marries his brother Gaheris. Other versions have it the other way around.
    • Lancelot is double cousins with Lionel and Bors — his father is brothers with their father, and his mother is sisters with their mother.

    Tabletop Games 
  • The Clothar race in Traveller always has these. Clothar are born as a brother-sister pair of mindlinked twins, and each pair marries another pair, creating what amounts to a quadruple marriage rather then a dual marriage. As each pair is telepathic, effectively everyone knows everything about the others' marriage.

    Video Games 
  • In Bubble Bobble, twin brothers Bubblun and Bobblun are dating a pair of sisters named Betty/Peb and Patty/Pab.
  • The Fire Emblem games have several potential cases:
    • In Fire Emblem: The Sacred Stones, the player can pair Prince Ephraim with Princess Tana and Ephraim's twin sister Princess Eirika with Tana's older brother Prince Innes.
    • Also doable in the second generation of Genealogy of the Holy War with, well, any two brother-sister pairs, but notably Arthur with Phee and Ced with Tine. This can also potentially be two pairs of Kissing Cousins if Patty is with Lester and Febail with Lana. Even more in the case of the last two couples together; their mothers Edain and Briggid were identical twin sisters, so this involves marrying two pairs of genetic half-siblings to each other.
      • Can be done in many varieties in Fire Emblem: Awakening with the second generation, all involving Lucina, Chrom!Inigo or Chrom!Brady and a family consisting the male Avatar and a woman who has a son. (For example, Avatar!Gerome can marry Lucina and his younger sister Morgan goes for Chrom!Inigo or Chrom!Brady, or Avatar!Inigo can marry Lucina and Morgan marries Chrom!Brady. Add Owain to the mix and things can get even zanier.)
      • In the DLC route of Fire Emblem Fates, it's possible to do up to a quadruple version of this trope by getting the Nohr and Hoshido royal families to marry each other. There are four possible combinations: the first would have Elder Princes and Elder Princesses (Ryoma/Camilla and Xander/Hinoka) plus Younger Princes and Younger Princesses (Takumi/Elise and Leo/Sakura), the second has Elder Princes and Younger Princesses (Xander/Sakura and Ryoma/Elise) plus Elder Princesses and Younger Princes (Takumi/Camilla and Leo/Hinoka), and the other two have one Elder Prince with an Elder Princess and the other with a Younger Princess while the Younger Princes reverse which is paired with Elder and which with Younger (Xander/Hinoka, Ryoma/Elise, Leo/Sakura, and Takumi/Camilla or Xander/Sakura, Ryoma/Camilla, Leo/Hinoka, and Takumi/Elise). Plus there are even more variations where only two or three of the siblings marry each other. For a Birthright only example, one could marry Hinoka and Sakura to ninja brothers Kaze and Saizo (then marry their children Asugi and Midori to each other). And of course, there's the possibility to pull this off with the second generation. If Azura marries a man who produces a daughter, and the female Avatar does the same, then Azura's son Shigure can marry the Avatar's daughter, and the Avatar's son Kana can marry Azura's daughter. For bonus points Kissing Cousins comes into play: the Avatar and Azura are cousins, meaning their children are second cousins to each other. Conquest and Revelation have a Double Subverted example: the Male Avatar can marry Flora and either Xander or Leo can marry her sister Felicia. Subverted in that the Avatar is not blood-related to Xander and Leo. Double subverted in that the Avatar only learned this recently, and certainly still regards Xander and Leo as his brothers. The same Avatar/Flora pairing can also create a straighter version in Revelation, as Ryoma and Takumi are also recruitable here and can be paired with Felicia. "Straighter" in that it's only a single subversion, as Ryoma and Takumi aren't blood relatives of the Avatar either. However, this time the Avatar doesn't know that. Birthright also has a subverted example if the Female Avatar replaces one of the women in the above-mentioned ninja example for the same reason it's subverted with a Ryoma/Takumi example.
  • A possible marriage outcome in Long Live the Queen. If Elodie has shown interest in Brin, Duchess of Hellas who is a lesbian by preference, she suggests that they can be together if Brin marries Elodie's father and Elodie marries Brin's brother. This gets very confusing for any resulting children.

    Web Animation 

    Web Comics 
  • In Erstwhile, when Rose Red confides her problems with marrying when she and her sister ought to always share, the bear suggests that she marry a man with a brother who can marry her sister. The bear is a transformed prince, and yes, he has a brother.
  • Planned in Homestuck: According to their destiny, Rose must marry John while her twin Dave must marry John's twin Jade. Whether this will actually come to pass, or whether they will fight fate remains to be seen, particularly since Rose is already in a relationship with Kanaya. Note that "fate" here means "teenage alien with a shipping grid", and the only reason he's bothering is that the kids are the last surviving humans except for alternate-universe teenage versions of their parents.
  • In Trial of the Sun, Rennin and Caliosis end up marrying each other's sisters: Rennin set up his good friend with his sister out of gratitude, and much later married Cal's sister Filumena when Filumena's marriage prospects had otherwise weakened.

    Western Animation 

    Real Life 
  • Anthropologists call (one type of) this Brother-Sister Exchange, such as the Mundugumor of New Guinea.
  • Romans, especially the rich upper classes, would often do this, with daughters as bargaining pieces to enforce alliances. Just look at the family of the Julio Claudian Emperors, for example. This tradition carried over to the medieval era, with most royal families engaging in this.
  • The most famous Siamese Twins (now referred to as Conjoined Twins), Chang and Eng Bunker, married sisters.
  • It doesn't come up in her own books, but Laura Ingalls Wilder's parents were the second of three marriages between their families: Uncle Henry was Ma's brother and his wife, Aunt Polly, was Pa's sister, while Aunt Eliza was Ma's sister and Uncle Peter was Pa's brother.
  • There was a question on Yahoo Answers once (quite possibly Trolling, or at least posing a thought experiment) about a pair of identical twins who'd married another set of identical twins and wanted to set up an Arranged Marriage between their respective children. Once you've gotten over the initial instinct to reach for the Brain Bleach and done a bit of basic maths, you realise the kids in question would be, genetically speaking, full siblings. Yeeah. There was a case in the UK of one set of identical twins marrying another, not that they planned it like that. One marriage apparently ended in divorce.
  • Sigmund Freud's wife Martha Bernays was the sister of Ely Bernays, who married Sigmund's sister, Anna Freud (making public relations pioneer Edward Bernays Freud's "double nephew").
  • These marriages were popular among peasants in early modern France in the brother-and-sister marry brother-and-sister form. Whereupon the two brides, in lieu of a dowry, would sign over to each other their respective inheritance rights.
  • Averted in the case of the Dionne quintuplets (the first-ever surviving set of quintuplets, all girls): Dr. Allan Roy Dafoe, who had charge of them through their tenth year, was convinced that they would never marry because there was no set of identical male quintuplets. Three did eventually marry men not related to one another; one became a nun (and died young, to boot); and the fifth devoted herself to her work and never married.
  • Almost happened with Napoléon Bonaparte and his elder brother Joseph: Joseph married Julie Clary, the daughter of a wealthy silk merchant, in 1794 and Napoleon fell in love with and became engaged to Désirée, Julie's younger sister. However, Désirée's parents did not want another Bonaparte son-in-law; instead, Napoleon met and married the attractive and influential widow Joséphine de Beauharnais, leaving Désirée to marry General Bernadotte and eventually become Queen of Sweden.
  • On 24 and 26 December 1793, Crown Prince Frederick William of Prussia (later King Frederick William III) and his next-eldest brother Ludwig (or Louis) married two sisters, Princesses Louise and Friederike of Mecklenburg-Strelitz. Frederick William married Louise, Louis married Friederike.
    • Two of Frederick William's sons, William (later Kaiser Wilhelm I) and Charles, also married sisters, with William marrying Princess Augusta of Saxe-Weimar-Eisenach and Charles marrying her older sister Marie.
    • Another example from that era: César and Léopold Berthier, the younger brothers of Napoleon's chief of staff, married a pair of sisters.
  • Prince Edward, Duke of Kent and Strathearn, was the paternal uncle of Princess Charlotte of Wales. Charlotte was married to Prince Leopold of Saxe-Coburg-Saalfeld, and his sister, Princess Victoria, married Duke Edward. Their only child later became Queen Victoria. This is a variant on the trope, however; Princess Charlotte died in 1817 at the age of 21, and Prince Edward didn't marry Princess Victoria until 1818. (Charlotte was an only child, and her death caused the threat of a Succession Crisis as none of her uncles and aunts had legitimate children.)
  • Prince Harry and Pippa Middleton allegedly grew close during their siblings' wedding preparations (and the media jumped on board), but nothing came of it, and both eventually married other people.
  • Louis XIII of France married the Spanish princess Anne of Austria, while his sister Elisabeth married Anne's brother Philip IV of Spain. Their respective children, Louis XIV of France and Maria Theresa of Spain, later married each other; this meant that their child Louis, the Grand Dauphin, had as many great-grandparents as grandparents.
  • Twice over for the four beautiful daughters of Ramon Berenguer IV, Count of Provence: Marguerite and Beatrice married one set of brothers, Louis IX of France and Charles I of Naples and Sicily, while Aliénor and Sanchia married another set of brothers, Henry III of England and Richard of Cornwall, King of the Romans. With the exception of Sanchia and Richard's, all of these were Perfectly Arranged Marriages.
  • Marriages between sets of identical twins are surprisingly common, with a few dozen documented in just the past decade.
    • One such marriage was apparently arranged between aristocratic twins César and Constantin Faucher, and a pair of equally aristocratic twin sisters, but circumstances decided otherwise as the sisters emigrated with their parents, while the brothers embraced the Republic.
  • Andrew and Michael Tierney from Human Nature married sisters.
  • Defied in Filipino marriage traditions, where there is a term called "sukob," where a sibling must wait for a full year before they can get married, and it is considered a disastrous thing for siblings to get married at the same time.
  • Yeonsan-gun of Joseon married Lady Sin from the Geochang Sin clan. Yeonsan's half-brother I Yeok (the future King Jungjong) married Lady Sin's niece.
  • King Taejo of Goryeo married Lady Dongsanwon of the Suncheon Bak clan. Taejo's son Jeongjong married two of Dongsanwon's sisters. This meant Jeongjong was both Dongsanwon's stepson and brother-in-law, and his son Prince Gyeongchunwon was both Dongsanwon's nephew and step-grandson.
  • Another set of weird marriages in the Goryeo royal family: King Yejong married Queen Sundeok of the Incheon I clan and had a son with her. That son, King Injong, grew up to marry two of Sundeok's younger sisters. Which means he was their nephew as well as their husband, and their sister became their mother-in-law.
  • Abdullah I of Jordan (great-grandfather of current King Abdullah II) married Musbah bint Nasser, while his younger brother Faisal I of Iraq married Musbah's twin sister, Huzaima. For bonus points, Abdullah and Faisal were first cousins of Musbah and Huzaima.
  • England's Richard III was married to Anne Neville, while his older brother George, Duke of Clarence was married to Anne's older sister, Isabel Neville, a situation that came about quite dramatically during the Wars of the Roses. Anne and Isabel's father, Richard Neville, Earl of Warwick, had helped Richard and George's oldest brother become King Edward IV only to become resentful over Edward's favoring of his wife's middle class family. Warwick was the foster father of both George and Richard and thus the boys grew up in the same social circle as Warwick's daughters but Edward forbid matches between them. Warwick, who desired the matches, eventually rebelled and George joined him, marrying Isabel without the King's permission. Richard, however, stayed loyal to Edward. Warwick eventually switched sides and married Anne to the Lancastrian heir to the throne, and George returned to the Yorkist side. When Warwick and the Lancastrian prince were killed, fourteen-year-old widow Anne was placed in the care of George and Isabel. The sisters' had a fortune which was supposed to be split between them, but George wanted the entirety of it for himself. Richard pursued Anne, and legend has it that George hid her in the kitchens as a servant to prevent them seeing one another. Richard eventually found her, and after a bitter negotiation, Richard and Anne married. Despite all the drama, and all four parties dying young, evidence suggests both couples were Happily Married.