• Before making a single edit, Tropedia EXPECTS our site policy and manual of style to be followed. Failure to do so may result in deletion of contributions and blocks of users who refuse to learn to do so. Our policies can be reviewed here.
  • All images MUST now have proper attribution, those who neglect to assign at least the "fair use" licensing to an image may have it deleted. All new pages should use the preloadable templates feature on the edit page to add the appropriate basic page markup. Pages that don't do this will be subject to deletion, with or without explanation.
  • All new trope pages will be made with the "Trope Workshop" found on the "Troper Tools" menu and worked on until they have at least three examples. The Trope workshop specific templates can then be removed and it will be regarded as a regular trope page after being moved to the Main namespace. THIS SHOULD BE WORKING NOW, REPORT ANY ISSUES TO Janna2000, SelfCloak or RRabbit42. DON'T MAKE PAGES MANUALLY UNLESS A TEMPLATE IS BROKEN, AND REPORT IT THAT IS THE CASE. PAGES WILL BE DELETED OTHERWISE IF THEY ARE MISSING BASIC MARKUP.


WikEd fancyquotes.pngQuotesBug-silk.pngHeadscratchersIcons-mini-icon extension.gifPlaying WithUseful NotesMagnifier.pngAnalysisPhoto link.pngImage LinksHaiku-wide-icon.pngHaikuLaconic

Bob and Janet are siblings. So are Spencer and Alice. Alice marries Bob, while Janet falls in love with Spencer. This would also work if Alice and Janet were sisters, and Bob and Spencer were brothers. Then Alice would marry one brother, and Janet would marry the other. In other words, a 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.

This can lead to a major Tangled Family Tree as the children of one couple are "double cousins" of the children of the other. Since they are as genetically similar as half-siblings, Kissing Cousins is even more discouraged in such cases. This gets ramped up in cases of one or two sets of identical twins being involved, for obvious reasons.

Not to be confused with Brother-Sister Incest or Settle for Sibling (although overlap with the latter is certainly not impossible).

Examples of Double In-Law Marriage include:

Anime and Manga


  • 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.

Fan Fiction

Fairy Tales

  • The eponymous sisters of "Snow White and Rose Red" married princes who were brothers.
  • In King Arthur mythology, brothers Gareth and Gaheris married sisters Lyonesse and Lynet.


  • Jane Austen loves this trope:
    • 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.
    • 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 Steele were in the way).
    • 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.
    • 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.
  • At the very beginning of A Song of Ice and Fire, 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. Later Catelyn Stark makes a contract with Walder Frey for Robb and Arya to marry two Frey siblings. And as near everyone knows, all of this backfired terribly.
  • 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, they all lived Happily Ever After while the main plot moved on...
  • 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.
  • In Amy Tan's The Bonesetter's Daughter, sisters Lu Ling and Gao Ling marry brothers Edwin and Edmund Young.
  • 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.
  • 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.
  • Mentioned in an aside in To Kill a Mockingbird, although not actually featured. Atticus mentions the concept of double cousins to Scout, saying "two brothers married two sisters." She and Dill work on figuring it out, and reason that if Dill had a sister whom he married, and Jem and Scout got married, their kids would be double cousins. Only off by a little bit there...
  • 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.
  • In the novel Malevil, the main character's father and uncle married a pair of sisters.
  • 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.
  • 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.)
  • 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.
  • In Jacqueline Wilson's Double Act, Garnet has always assumed she and her twin sister Ruby would marry a pair of twin boys.

Live Action TV

  • Roseanne: Darlene and Becky Conner married David and Mark Healy, respectively.

 David: Thanks for making me and my girlfriend related.

    • 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. To the point where when Darlene and David get engaged Roseanne celebrates the fact that they are officially the most redneck white trash in town.
  • In Lost in Austen, after Mr. Collins marries Jane, he tries to marry his brothers off to the younger Bennett sisters. It doesn't quite work out.
  • Into the West used this in the first episode.
  • Howe & 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.

Religion and Mythology

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

  • Fire Emblem:
    • Doable in the second generation of Genealogy of the Holy War with, well, near all two brother-sister pairs: i.e., having Phee marry Arthur and then following by her older brother Ced marrying Arthur's little sister Tine. Could potentially be two pairs of Kissing Cousins if one pairs Patty with Lester and Febail with Lana as well... and due to the genetics that come with their mothers (Brigid and Edain) being identical twins, both of the above pairings also count as Brother-Sister Incest.
    • Fire Emblem the Sacred Stones: pairing Ephraim with Tana and his twin sister Eirika with Tana's big brother Innes will finish in this. It certainly helps that Innes is implied to already be in love with Eirika, and the same goes to Tana towards Ephraim.
    • If both Chrom and a Male Avatar have two kids in Fire Emblem Awakening, this can be potentially done: i.e., a Lucina with a younger brother (Inigo or Brady) may marry a son of the Male Avatar (like Gerome or Laurent), while said brother marries his bro-in-law's little sister Morgan.
    • Not that hard to do in the Golden Path of Fire Emblem Fates, if the player arranges for the Nohrian Royals to marry the Hoshidan Royals of the opposite gender (i.e, Xander marries either Sakura or Hinoka, then Ryoma weds Camilla or Elise, and then Leo and Takumi marry the remaining princesses from the other realm). It may be possible if both of the Ninja twins Kaze and Saizo marry into the Hoshidan Royal Family (one brother marries Hinoka, the other marries Sakura), or if the Male Avatar marries Flora and her twin sister Felicia marries either of the Hoshidan or Nohrian Princes (though the Male Avatar isn't related by blood to them, he considers them his brothers nevertheless.)
  • A sidequest in Final Fantasy XII revolves around preventing this situation. A group of seven Archadian nobles who are all brothers are trying to force a group of seven sisters who work as airship stewardesses to marry them.


  • In Sakana, this is heavily suggested with the Sakana brothers and the Yamamoto sisters. The younger siblings (Jiro and Chie) are pretty much an Official Couple, while Word of God has teased the older siblings (Taro and Mori) on multiple occasions, hinting at a love-hate relationship. The fact they're Birds of a Feather definitely helps.

Western Animation

  • A Disney Silly Symphony ended like this. Two feuding royal families make peace, and the king and the prince of one kingdom marry respectively the queen and princess of the other kingdom (by the way, they were also all anthropomorphic musical instruments).

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.
  • Averted by the Catholic Church. Such a marriage is forbidden under the affinity impediment.
  • 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').