History Main / BestFriendsInLaw

* ''Anime/PokemonTheSeries'': In many stories where Ash and Misty are the main pairing, it's not uncommon to find Tracey (one of Ash's friends) and Daisy (Misty's oldest sister) as the BetaCouple, thus making them this trope.

* ''Series/GameOfThrones'':
** King Robert Baratheon seemed to have something like this in mind when he visits his [[FireForgedFriends Fire-Forged Friend]] Lord Eddard Stark, to both name him TheConsigliere and to suggest marrying Ned's daughter Sansa to Robert's "son" Joffrey when they come of age (in truth, Joffrey is the incestuous offspring of the Queen and her brother, but Robert doesn't know that). Since Joffrey is in fact a total psycho, this didn't come to pass, and both Robert and Ned are killed off well before any marriage ceremony can take place. Posthumously, Robert's bastard son Gendry does become intimate with Ned's second daughter Arya.
** Considering that Ser Loras Tyrell had dreamed of marrying his boyfriend Lord Renly Baratheon from a very young age (Renly is the "bride" in "green and gold brocade" -- Renly wore a green brocade cloak to show his support for Loras at the jousting match), becoming brothers-in-law by Renly marrying Margaery was the only viable way for Renly to become part of Loras's family (and ''not'' Loras becoming part of Renly's family - there is a distinction), in addition to being motivated by politics. Since he was a young teen, Loras had hoped to make this fantasy come true in some form, and his family's lofty ambitions would later become the perfect excuse to permanently bond Renly to the Tyrells. Margaery is even willing to share Renly with Loras if it helps to get her pregnant. In the novels, Renly continued to use the traditional yellow-and-black sigil of House Baratheon after he declared himself king, but his TV counterpart adopts the green and gold of House Tyrell for his banner, which is Renly's way of demonstrating to Loras that he is indeed a Tyrell at heart if not in name, because Highgarden's colours are now his own. Loras makes a FreudianSlip in "Valar Morghulis" [[spoiler:("My sister Margaery, her husband was taken from ''us'' before...")]] which proves that he considers Renly to be his "husband."
** Margaery attempts to invoke this with her dear friend Sansa Stark, by trying to set up a betrothal between Sansa and Loras. The Lannisters interfere before it can get very far, but the girls enjoy the idea while it lasts.

May overlap with SettleForSibling or DoubleInLawMarriage. Not to be confused with making friends of your in-laws.

* ''Fanfic/JoJoNewUniverse'': [[Manga/JoJosBizarreAdventurePhantomBlood Jonathan Joestar and Robert E. O Speedwagon]] are just as much best friends as they are in the manga, but become in-laws when Robert would marry Jonathan's adopted sister, Lydia Twilight[[note]]A human version of [[WesternAnimation/MyLittlePonyFriendshipIsMagic Twilight Sparkle]][[/note]]. Likewise, Lydia would also be this trope to her {{Childhood Friend|s}} Erina Pendleton when the latter marry Jonathan.

* In ''Film/NottingHill'', William Thacker's sister, Honey, clearly believes in this trope when she first meets his date, famous actress Anna Scott:

* ''{{Literature/Emma}}'':
** Emma and Mr Knightley ''start'' this way, because her sister is married to his brother, and for all their little quibbles with each other they are clearly devoted friends. [[spoiler:They take this trope further, invoking DoubleInLawMarriage by getting married themselves at the end of the book.]]
** Emma grows very close to Frank Churchill, whose father is married to her former governess and mother substitute, making them unofficial stepsiblings as well as good friends. Frank is also extremely close with his stepmother, so the two of them fit the trope as well.

* In the ''Literature/LittleWomen'' series, Laurie eventually agrees with his best friend, Jo, that they're too similar to ever be happy as husband and wife. His SecondLove is Jo's youngest sister Amy, and Jo names her second son "Teddy," after her pet name for Laurie.

* In ''Literature/MansfieldPark'', Fanny eventually marries [[spoiler:her cousin Edmund]], and the book observes that her father-in-law completely adores her and goes to great lengths to have her visit. It's something of a variant on the trope, however, since [[spoiler:she was already his niece, and she grew up in his house so he adored her even prior to her romance with Edmund.]]

* ''Literature/NorthangerAbbey'':
** Catherine and Isabella initially hope to become this when Isabella gets engaged to Catherine's brother, James. [[spoiler: This ends when Isabella breaks James's heart and Catherine realizes Isabella's friendship wasn't quite so true.]]
** Isabella ''also'' hoped to double-down on this by getting Catherine together with her brother John, but Catherine was never attracted to him.
** Catherine and Eleanor Tilney actually do become this when Catherine marries Eleanor's brother, Henry.

* ''Literature/PrideAndPrejudice'':
** At the end of the book, Elizabeth marries Mr Darcy, and her sister Jane marries his best friend Mr Bingley. Elizabeth also develops this trope with her new sister-in-law Georgiana; the book notes that they grow to love each other dearly.
** Elizabeth's best friend Charlotte marries Mr Collins, Elizabeth's father's cousin (the exact relationship between them is never clarified), making them a form of this trope as well.

* At the end of ''Literature/SenseAndSensibility'', Colonel Brandon and Edward Ferrars are shown to be in the process of becoming close friends. They're in love with the Dashwood sisters, whom they marry by the last page, and the narrative explicitly describes them as becoming excellent friends even prior to the weddings because they have so much else in common, too.

* In the ''Franchise/StarWarsExpandedUniverse'', this trope becomes canon for Luke and Han Solo. Leia is likewise good friends with Luke's wife, Mara Jade.

** All twelve leads are immediate family ''and'' very close to all the others, so this happens whenever there's an in-law relationship. In particular, Phil and Mitchell, and Claire and Cam are siblings-in-law who enjoy spending time together independently of the rest of the family to pursue particular interests or hobbies. Phil and Cam might also count in this regard, since they're married to siblings from the same family and often hang out together.

*** In Generation 2, Sigurd's son Seliph can potentially end up with [[ChildhoodFriendRomance Lana, Larcei]], or Nanna (or their [[StaticRoleExchangeableCharacter replacement characters]] Muirne, Creidne, or Jeanne). All three of them are the sisters of his respective childhood friends Lester, Ulster, and Diarmuid (or Deimne, Dalvin, and Tristan). Larcei is also the cousin of Seliph's BigBrotherMentor, Shannan. Naturally, any possible pair up of this group will result in this. Nanna (who can also end up with Quan's son Leif) is also Eldigan's niece, so it's a double example. It's also possible to hook up the children of Azelle and Lex, or Alec and Naoise. [[spoiler:While it's ''very'' tricky, it's also possible to pair Seliph's half-sister Julia up with any of the possible male characters.]]

** In ''VideoGame/FireEmblemTheBlazingBlade'' the best friend duos of Sain and Kent or Eliwood and Hector can become this if they both marry one of the Pegasus sisters Florina, Fiora and Farina.

* ''VideoGame/GalaxyAngelII'' has this potentially happen depending on the player choices regarding Tact and Kazuya. The player decides who is Tact's wife from the ''VideoGame/GalaxyAngel'' original trilogy, and depending who Kazuya ends up romancing, he can end up as Tact's brother-in-law if he pursues Rico and Tact is married to Milfie, or as his son-in-law if he pursues Nano-Nano and Tact is married to Vanilla.

* ''WebAnimation/{{Otakebi}}'': [[https://www.youtube.com/watch?v=AimgFqC5f10 Mami]] is in a good relationship with her mother-in-law. The women become closer after they get a divorce from their respective husbands and Mami considers her ex-mother-in-law to be her only family she have.

* [[https://en.wikipedia.org/wiki/Marie_Th%C3%A9r%C3%A8se_Louise_of_Savoy%2C_Princesse_de_Lamballe Princess Marie-Louise of Savoy]], the Princesse de Lamballe, is best remembered by history for having been a close friend of UsefulNotes/MarieAntoinette (and being beheaded as part of that whole mess). She had this going with her father-in-law, the Duke of Penthièvre, who even consoled her when his son was unfaithful to her on more than one occasion. Her husband died less than two years after their ArrangedMarriage, and she intended to become a nun; but she and the Duke were such great friends that he persuaded her to instead remain in the family home and for all intents and purposes be his daughter. She agreed, joining him in much of his charity work, and they remained close until she was killed in the French Revolution.

* This was one of the biggest motivations of marriage for most of human history, to create alliances by marrying their children and creating kinship.

* In ''Manga/BloodyMonday'', Fujimaru's best friend Otoya is romantically involved with his younger sister Haruka. The two even get a double wedding at the final of the third season.
* In ''If I Could Reach You'', Uta sees her older brother Reiichi's wife Kaoru as a CoolBigSis, since they've [[ChildhoodFriends known each other since they were little]], and doesn't realize until it's too late that she's in love with Kaoru. Kaoru and Uta's mothers are also best friends, and the latter apparently feels responsible for a medical error that cost the former her life.
* Briefly discussed in ''Manga/KaguyaSamaLoveIsWar'' when it's revealed that [[spoiler:Moeha has a PrecociousCrush on Shirogane (her best friend Kei's older brother). Given that this is [[CuteAndPsycho Moeha]], she's also shown fantasizing about what kind of face Kei would make if she told her that she was (hypothetically) sleeping with him.]]
* ''Manga/KomiCantCommunicate'': Komi's mother, Shuuko, and her uncle's wife, Ryouko, are ''extremely'' good friends and always ecstatic when they can spend time together.

* In the ''Manga/DeathNote'' [[AlternateUniverseFic AU]] ''Fanfic/ThoseWhoStandForNothingFallForAnything'' Matsuda is Light's brother-in-law through his marriage with Sayu, and he ''thinks'' he and Light are this. Light, for his part, finds Matsuda to be annoying but convenient, and uses him when he needs to look sociable.
* In the ''Franchise/HarryPotter'' [[AlternateUniverseFic AU]] ''[[FanFic/ThreeSlytherinMarauders 3 Slytherin Marauders]],'' Snape and Lucius become this when [[spoiler: Snape adopts Harry and Lucius marries Petunia and adopts Dudley.]]
* Any ''WesternAnimation/MyLittlePonyFriendshipIsMagic'' story where [[TheHeroine Twilight]] marries / gets together with [[TheLancer Applejack]]'s brother, Big Macintosh, as many fans of the series consider Twilight and Applejack to be closest to each other among the Mane Six.

* The ''Franchise/LyricalNanoha''[=/=]''Manga/SailorMoon'' crossover ''Fanfic/WhiteDevilOfTheMoon'' does this with Hotaru and Alicia, who were adopted into the Takamachi and Harlaown families respectively after Nanoha and Fate had already started dating.

* [[VideoGame/TheLegendOfZeldaBreathOfTheWild Sidon and Link]] are this in ''Fanfic/{{Offspring}}''. Link is the widower of Sidon's sister Mipha.
* ''Fanfic/UltimateMisfits'': Jerrica and Pizzazz's mothers were best friends and their fathers were best friends too.

* [[VideoGame/DragonAgeII Varric and Hawke]] are this by the end of ''Fanfic/BeyondHeroes: Of Sunshine and Red Lyrium''.
* In several ''WesternAnimation/DannyPhantom'' fanfics, Danny's best friend Tucker ends up marrying his sister, Jazz, making them brothers-in-law. For Tucker, this applies two-fold in situations where Danny marries [[OfficialCouple Sam]].
* ''WesternAnimation/TheLoudHouse'':
** Some fan works feature Lincoln's best friend Clyde and his older sister Lynn as a couple, although it's more common for them to be merely dating rather than outright marrying.
** A few other fanfics have Lincoln and his friend Rusty become brothers-in-law via the marriage of their respective younger siblings (Lucy and the OneEpisodeWonder Rocky).
* Creator/FlowerPrincess11:
** In the author's ''WesternAnimation/EdEddNEddy'' fanfics, the Eds end up marrying their respective equivalents of the Kanker Sisters as adults, thus making them brothers-in-law (since all three of their wives are sisters).
** For their ''WesternAnimation/HeyArnold'' fanfics, [[spoiler:[[FanCreatedOffspring Andy Shortman (Arnold and Helga's son) and Kiara Johanssen (Gerald and Phoebe's daughter)]] get married as adults, thus making their parents in-laws (of some sort) to each other.]]

* In the Disney version of ''WesternAnimation/SleepingBeauty'', Phillip's dad (King Hubert) and Aurora's dad (King Stefan) are stated to be close friends and a big reason they want their kids to marry each other is to unite their kingdoms. Fortunately, it turns out to be a PerfectlyArrangedMarriage, with a touch of DramaticIrony.[[note]]He thought she was a regular peasant girl and she, unaware that she was a princess, fell in love with what she thought was a charming stranger.[[/note]]

* In the ''Franchise/StarWarsExpandedUniverse'', this trope becomes canon for Luke and Han Solo. Leia is likewise good friends with Luke's wife, Mara Jade.
* No one comes out and says it, but at the end of the ''Literature/{{Belgariad}}'' Durnik, Garion's oldest friend, technically becomes his uncle by marrying Polgara.

* In the ''Literature/LittleWomen'' series, Laurie eventually agrees with his best friend, Jo, that they're too similar to ever be happy as husband and wife. His SecondLove is Jo's youngest sister Amy, and Jo names her second son "Teddy," after her pet name for Laurie.
* In ''Literature/TheBigWave'', Kino and Jiya are childhood friends, and Jiya grows up to marry Kino's sister, Setsu.
* Creator/JaneAusten:
** ''Literature/PrideAndPrejudice'':
*** At the end of the book, Elizabeth marries Mr Darcy, and her sister Jane marries his best friend Mr Bingley. Elizabeth also develops this trope with her new sister-in-law Georgiana; the book notes that they grow to love each other dearly.
*** Elizabeth's best friend Charlotte marries Mr Collins, Elizabeth's father's cousin (the exact relationship between them is never clarified), making them a form of this trope as well.
** At the end of ''Literature/SenseAndSensibility'', Colonel Brandon and Edward Ferrars are shown to be in the process of becoming close friends. They're in love with the Dashwood sisters, whom they marry by the last page, and the narrative explicitly describes them as becoming excellent friends even prior to the weddings because they have so much else in common, too.
** ''{{Literature/Emma}}'':
*** Emma and Mr Knightley ''start'' this way, because her sister is married to his brother, and for all their little quibbles with each other they are clearly devoted friends. [[spoiler:They take this trope further, invoking DoubleInLawMarriage by getting married themselves at the end of the book.]]
*** Emma grows very close to Frank Churchill, whose father is married to her former governess and mother substitute, making them unofficial stepsiblings as well as good friends. Frank is also extremely close with his stepmother, so the two of them fit the trope as well.
** In ''Literature/MansfieldPark'', Fanny eventually marries [[spoiler:her cousin Edmund]], and the book observes that her father-in-law completely adores her and goes to great lengths to have her visit. It's something of a variant on the trope, however, since [[spoiler:she was already his niece, and she grew up in his house so he adored her even prior to her romance with Edmund.]]
** In ''Literature/NorthangerAbbey'':
*** Catherine and Isabella initially hope to become this when Isabella gets engaged to Catherine's brother, James. [[spoiler: This ends when Isabella breaks James's heart and Catherine realizes Isabella's friendship wasn't quite so true.]]
*** Isabella ''also'' hoped to double-down on this by getting Catherine together with her brother John, but Catherine was never attracted to him.
*** Catherine and Eleanor Tilney actually do become this when Catherine marries Eleanor's brother, Henry.
* Laurie Polk, the protagonist of one story in the GenreAnthology mystery collection ''Five-Minute Mysteries 3: another 40 cases of murder and mayhem for you to solve,'' is investigating the death of his brother-in-law Trent. Trent was Laurie's best friend since first grade and had a ChildhoodFriendRomance with Laurie's sister before marrying her. Consequently, [[DownerEnding Laurie is utterly devastated when he uncovers proof that his sister and an acquaintance almost certainly conspired to trick their respective spouses into getting trapped in a blizzard and freezing to death.]]
* ''Literature/BridgetJones'': The parents of Bridget and Mark have been close friends for a long time and have been trying to set the two up together. They fail, succeed, and fail until succeeding again.
* ''Literature/TheGreatGreeneHeist'': Charlie and Jackson have been best friends and partners in crime since before Charlie's sister Gaby and Jackson developed feelings for each other.
* The [[Literature/MatthewScudder Lawrence]] [[Literature/BernieRhodenbarr Block]] short story ''Keller on Horseback'' features a man who married the daughter of his best friend and surrogate father, Lyman Crowder. This is deconstructed though, as their marriage becomes an AwfulWeddedLife but neither can bear to disappoint Crowder by getting a divorce, so someone who wants them to get divorced hires a hitman to kill Crowder.
* In ''Literature/{{Overenskommelser}}'' by Creator/SimonaAhrnstedt, Beatrice/Seth and Sofia/Johan have this kind of relationship. Beatrice and Sofia are cousins, while Seth and Johan were close friends even before they met the Löwenström girls. Magdalena and Gabriel in "De skandalösa" have a similar relationship with Gabriel's sister Nora and [[spoiler:her gay lover Venus]].
* Literature/LordPeterWimsey's FriendOnTheForce, Charles Parker, falls in love with Wimsey's sister Lady Mary during ''Clouds of Witness'' and later marries her.
* In the ''[[Creator/MaryGrantBruce Billabong]]'' series, Jim and Wally are best friends and then become brothers-in-law when Jim's younger sister and Wally fall in love and get married.
* ''Literature/TheScholomance:'' Chloe's father (an indie kid) and her maternal uncle (an enclaver) were allies when they attended the Scholomance together. Her uncle introduced her dad to his sister after they made it out alive, leading to their marriage.

* ''Literature/DancingAztecs'': Mel, Frank, and Floyd are the husbands of Jerry's two sisters, and Frank's brother respectively, and the four get along pretty well, run various scams together, and are equal partners in the statute hunt.
* ''Literature/MitchTobin'': Ernie Rembek's brother-in-law Frank Donner is a trusted crony of his and a member of his crime syndicate.
* ''Literature/BazilBroketail'': Played straight with Eilsa's father Ranard, who comes to respect Relkin as a man and a warrior during their fight against the Padmasan invasion and approves of his relationship with his daughter. Averted with all her other relatives — especially her aunt Kiri — who despise Relkin for who he is and constantly try to discourage Eilsa from marrying him, offering her better situated and wealthier candidates.
* It's implied near the end of ''Literature/TheElenium'' that Sparhawk's daughter Danae will marry his squire Kurik's son Talen. [[spoiler:Kurik has died by this point, so it's too late for him to be this trope with Sparhawk, but Sparhawk also considers Talen himself a friend so the trope will apply to them.]]
* ''Literature/MyNextLifeAsAVillainessAllRoutesLeadToDoom''
** Catarina has this relationship with two of her ChildhoodFriends. Mary is engaged to Alan, the twin brother of Katarina's fiance Geordo. This gets complicated since in the series which royally put the game off-rails thanks to Catarina's change of personality and her active ways to avoid her doom, Mary ''and'' Alan have feelings towards Catarina, which Geordo doesn't appreciate. Meanwhile, Sophia actively tries to hook Catarina up with her older brother Nicol, who has feelings for her but doesn't act on it out of respect for Geordo.
** This also applies within the unaltered game scenario as well. From what little Catarina knew of Nicol's route, getting the good ending requires the player to have a very close relationship with Sophia.

* ''Series/GameOfThrones'':
** King Robert Baratheon seemed to have something like this in mind when he visits his [[FireForgedFriends Fire-Forged Friend]] Lord Eddard Stark, to both name him TheConsigliere and to suggest marrying Ned's daughter Sansa to Robert's "son" Joffrey when they come of age (in truth, Joffrey is the incestuous offspring of the Queen and her brother, but Robert doesn't know that). Since Joffrey is in fact a total psycho, this didn't come to pass, and both Robert and Ned are killed off well before any marriage ceremony can take place. Posthumously, Robert's bastard son Gendry does become intimate with Ned's second daughter Arya.
** Considering that Ser Loras Tyrell had dreamed of marrying his boyfriend Lord Renly Baratheon from a very young age (Renly is the "bride" in "green and gold brocade" -- Renly wore a green brocade cloak to show his support for Loras at the jousting match), becoming brothers-in-law by Renly marrying Margaery was the only viable way for Renly to become part of Loras's family (and ''not'' Loras becoming part of Renly's family - there is a distinction), in addition to being motivated by politics. Since he was a young teen, Loras had hoped to make this fantasy come true in some form, and his family's lofty ambitions would later become the perfect excuse to permanently bond Renly to the Tyrells. Margaery is even willing to share Renly with Loras if it helps to get her pregnant. In the novels, Renly continued to use the traditional yellow-and-black sigil of House Baratheon after he declared himself king, but his TV counterpart adopts the green and gold of House Tyrell for his banner, which is Renly's way of demonstrating to Loras that he is indeed a Tyrell at heart if not in name, because Highgarden's colours are now his own. Loras makes a FreudianSlip in "Valar Morghulis" [[spoiler:("My sister Margaery, her husband was taken from ''us'' before...")]] which proves that he considers Renly to be his "husband."
** Margaery attempts to invoke this with her dear friend Sansa Stark, by trying to set up a betrothal between Sansa and Loras. The Lannisters interfere before it can get very far, but the girls enjoy the idea while it lasts.

* On ''Series/DoctorWho'', [[spoiler:the Doctor]] marries [[spoiler:River Song]] (a.k.a. [[spoiler:Melody Pond, Amy and Rory's daughter from the future]]). [[spoiler:Amy]] (who predicted the match a season and a half earlier) has a funny moment when she realizes that, as a result of it, she's now [[spoiler:the Doctor]]'s mother-in-law!
* Subverted with Jim and Andy in ''Series/AccordingToJim'': They didn't start off as friends but become this after Jim marries Andy's sister. Jim is also really close to his mother-in-law, to the point where Andy thinks she prefers him as a son.
* In the pilot episode of the original ''Series/{{Battlestar Galactica|1978}}'', Apollo and Starbuck were heading this direction when the latter was planning to be sealed to Athena, but then he broke it off with her following the Destruction of the Colonies. Apollo seems to understand this for the most part, [[TheCasanova knowing him]]...
* ''Series/{{Scrubs}}'':
** In the finale, J.D. pictures his and Kim's son, Sam, and Turk and Carla's daughter, Izzy, all grown up and revealing to him and Turk that they're engaged to get married. Cue {{Squee}}ing J.D. and Turk. Notable in that, [[ImagineSpot unlike J.D.'s other fantasies]], this is part of a montage that J.D. and the finale strongly imply ''will'' eventually happen. Given by season 9, two of his visions from that montage (his and Elliot's wedding, and her being pregnant with his second child) have happened already, [[FutureShadowing it probably will]].
** Dr. Cox and Ben Sullivan were this. Their friendship withstood Cox's divorce from Ben's sister.

* In the series finale of ''Series/WillAndGrace'', Will and Grace themselves become this after their children marry.
** ...which turned into AllJustADream when the series became UnCancelled in 2017.
* On ''Series/{{Heroes}}'', Hiro's best friend Ando has been in love with/crushing on his older sister Kimiko since they were kids. Thanks to some meddling in the past by Hiro, Ando and Kimiko are engaged and Hiro is absolutely delighted.
* {{Inverted}} in ''Series/BreakingBad''; there's no indication that Hank and Walt were ever friends before marrying sisters Skyler and Marie, but by the time of the series, Walt has no closer male friend, and Hank's only other close male relationship is [[FireForgedFriends Steve Gomez]]. It makes it heartbreaking when [[WeUsedToBeFriends Hank finds out about Walt's drug dealing]], especially since Walt continues to [[ThickerThanWater consider Hank "family"]] and one of the few people for whom [[EvenEvilHasStandards he would never consider arranging a convenient "accident"]], even if the alternative is being caught or killed himself.
* ''Series/ModernFamily'' sets this up by its very nature:
** All twelve leads are immediate family ''and'' very close to all the others, so this happens whenever there's an in-law relationship. In particular, Phil and Mitchell, and Claire and Cam are siblings-in-law who enjoy spending time together independently of the rest of the family to pursue particular interests or hobbies. Phil and Cam might also count in this regard, since they're married to siblings from the same family and often hang out together.
** Jay shares this relationship with one son-in-law (Cam) but not the other (Phil). Poor Phil obviously feels snubbed by this, though it becomes increasingly apparent that Jay cares for him much more than he lets on; to be fair, he's often harsh to Cam too (particularly when referring to him as "my son's friend" in front of his buddies), and only really bonds with him over their shared love of sports.
** One of the reasons Phil is such a big ShipperOnDeck for Haley and Andy is clearly that he would like nothing better than to have Andy as a son-in-law. The feeling is obviously mutual, as Andy idolises Phil.

* [[FrankensteinsMonster Herman Munster]] and his father-in-law [[{{Dracula}} Grandpa]] in ''Series/TheMunsters'' are prone to getting involved in various schemes and shenanigans, usually behind Lily’s back. This carries over in ''The Munsters Today'', but is subverted in that Grandpa possesses a more spiteful opinion of Herman.
* Blair and Serena on ''Series/GossipGirl'' become this after Blair marries Chuck, Serena's adoptive brother.
* While there's no ''technical'' relationship between them, Riley of ''Series/GirlMeetsWorld'' calls her father's HeterosexualLifePartner "Uncle Shawn." When he begins dating Riley's best friend Maya's mother, she's overjoyed that they're going to be family.
-->'''Riley:''' We were like sisters, and now we'll be cousins! *''{{beat}}''* Wait a second. That's ''less.''
* ''Series/TheOC'': Taylor and Summer might well be heading for this, judging from the look the former exchanges with Ryan at the latter's wedding to Seth during the series finale's FlashForward, Ryan and Seth being foster brothers.
* The series finale of ''Series/TheGoldenGirls'' does a version of this for Blanche and Dorothy. The divorced Dorothy gets married to Blanche's widowed uncle, making them step-aunt and step-niece as well as best friends.

* On ''Series/TheMarvelousMrsMaisel'', Imogene suggests to her bestie Midge that they set up their two young children.

* In Myth/ClassicalMythology, Orestes was raised alongside his cousin, Pylades, after his mother and her lover tried to kill him as a child. Pylades accompanies him throughout his revenge quest and subsequent madness, enduring exile from his own homeland and even offering to die in Orestes' place in ''Iphigeneia in Tauris.'' Orestes' sister Electra is also with them through most of these ordeals, and Apollo himself instructs them to get married.

* In ''VideoGame/YsTheOathInFelghana'', the PlayerCharacter's best friend (whose homeland/hometown the game's set in) mentions this trope in regards to his childhood best friend Chester's sister, then notes that she'll probably end up with TheHero.

* ''Franchise/DragonAge'' has a couple:
** It hasn't really come up in the games themselves, but the first tie-in comics for the series give this relationship to Varric Tethras and Maevaris Tilani. Mae was betrothed to Varric's cousin Thorold, who was killed before the marriage could take place; but by the intricacies of dwarven inheritance law, she is nevertheless considered his widow, and it's clear that Varric regards her as family and they are good friends.
** In the backstory of the royal family of Ferelden, Calenhad Theirin - the first king of a united Ferelden - was married to Mairyn, the daughter of Arl Myrddin, one of his most loyal supporters and closest friends. They were this trope for the first several months of the marriage; unfortunately, it did not end happily. The pregnant Mairyn discovered Calenhad's infidelity with his general, Lady Shayna (a {{love potion}} is said to have been involved) and fled to her father, who later killed Lady Shayna. Calenhad reluctantly challenged Myrddin to a duel to avenge her, and Myrddin was killed.

* In ''VideoGame/TheLegendOfZeldaBreathOfTheWild'', this was ''almost'' the case with [[spoiler:Link and Prince Sidon, as Sidon's sister Mipha was in love with Link. But Mipha was killed before she could present the Zora Armor to Link to make any marriage promise official. Played with even further in that Sidon doesn't really get to know Link until a century after Mipha's death; nevertheless, his sister's feelings, combined with Link's heroics against Divine Beast Vah Ruta, still result in Sidon coming to view the Hylian as his best friend.]]
* ''VideoGame/GalaxyAngelII'' has this potentially happen depending on the player choices regarding Tact and Kazuya. The player decides who is Tact's wife from the ''VideoGame/GalaxyAngel'' original trilogy, and depending who Kazuya ends up romancing, he can end up as Tact's brother-in-law if he pursues Rico and Tact is married to Milfie, or as his son-in-law if he pursues Nano-Nano and Tact is married to Vanilla.

* ''WesternAnimation/TheFlintstones'' animated special ''I Yabba-Dabba-Do'' centers around Pebbles and Bamm-Bamm getting married, making the Flintstones and Rubbles in-laws.
* ''WesternAnimation/MyLittlePonyFriendshipIsMagic'': Twilight Sparkle had Princess Cadance as a foal-sitter and considered her a friend, but they fell out of contact. The next she hears from Cadance is a wedding announcement -- and the groom is Twilight's older brother Shining Armor.

* On ''WesternAnimation/AmericanDad'', one of the only recurring {{Love Interest}}s that Steve has is his friend Toshi's younger sister Akiko. His other friend, Snot, sometimes has a PrecociousCrush on Hayley, though not much comes of that.

** A few other fanfics have Lincoln and his friend Rusty become brothers-in-law of sorts via the marriage of their respective younger siblings (Lucy and the OneEpisodeWonder Rocky).

** Some fans and their works feature Lincoln's best friend Clyde and his older sister Lynn as a couple, although it's more common for them to be merely dating rather than outright marrying.

* Some ''WesternAnimation/TheLoudHouse'' fanfics have Lincoln and his friend Rusty become brothers-in-law via the marriage of their respective younger siblings (Lucy and the OneEpisodeWonder Rocky).

** In the author's WesternAnimation/EdEddNEddy-fanfics, the Eds end up marrying their respective Kankers as adults, thus making them brothers-in-law (since all three of their wives are sisters).
** For the author's WesternAnimation/HeyArnold-fanfics,[[spoiler: Andy Shortman (Arnold and Helga's son) and Kiara Johanssen (Gerald and Phoebe's daughter) get married as adults, thus making their parents in-laws (of some sort) to each other.]]

* ''LightNovel/MyNextLifeAsAVillainessAllRoutesLeadToDoom''
** Catarina has this relationship with two of her ChildhoodFriends. Mary is engaged to Alan, the twin brother of Katarina's fiance Geordo. This gets complicated since in the series which royally put the game off-rails thanks to Catarina's change of personality and her active ways to avoid her doom, Mary ''and'' Alan have feelings towards Catarina, which Geordo doesn't appreciate. Meanwhile, Sophia actively tries to hook Catarina up with her older brother Nicol, who has feelings for her but doesn't act on it out of respect for Geordo.
** This also applies within the unaltered game scenario as well. From what little Catarina knew of Nicol's route, getting the good ending requires the player to have a very close relationship with Sophia.

** In the finale, J.D. pictures his and Kim's son, Sam, and Turk and Carla's daughter, Izzy, all grown up and revealing to him and Turk that they're engaged to get married. Cue {{Squee}}ing J.D. and Turk. Notable in that, [[ImagineSpot unlike J.D.'s other fantasies]], this is part of a montage that J.D. and the finale strongly imply ''will'' eventually happen.

* The ''WesternAnimation/TheFlintstones'' animated special ''I Yabba-Dabba-Do'' centers around Pebbles and Bamm-Bamm getting married, making the Flintstones and Rubbles in-laws.

* ''VideoGame/GalaxyAngel'' has this potentially happen in the second trilogy. It all depends on player choices regarding Tact and Kazuya, though Tact's case can also invoke this on female Rune Angels Rico and Nano should he marry Milfie or Vanilla (to tie Kazuya into the equation he has to romance Rico for Milfie and Nano for Vanilla).

* In ''WesternAnimation/TheSimpsons'' FlashForward episode "Holidays of Future Passed," Lisa has married Bart's lifelong BestFriend Milhouse. It's a less-than-idyllic example as the two have DeadSparks and she wonders if she should have married Nelson--which means ''both'' of her options were [[BullyTurnedBuddy best friends of Bart]].

[[folder:Web Animation]] ''WebAnimation/EtraChanSawIt'': One story has Yuri and Tsutsuji as childhood friends who grow up to marry each other's older brothers. Tokusa is Yuri's older brother and Katsura is Tsutsuji's older brother.

** The non-canon "Kids" OVA of the [[Anime/FullmetalAlchemist the 2003 anime]] depicts three of Ed's grandkids. Two [[IdenticalGrandchild look exactly like]] Edward and Alphonse, while the third resembles ''Winry''. This means that either Edward or Alphonse married Winry (or [[spoiler:her Earth counterpart]]).

[[/folder]]

* Briefly discussed in ''Manga/KaguyaSamaLoveIsWar'' when it's revealed that [[spoiler:Moeha has a PrecociousCrush Shirogane (her best friend Kei's older brother). Given that this is [[CuteAndPsycho Moeha]], she's also shown fantasizing about what kind of face Kei would make if she told her that she was (hypothetically) sleeping with him.]]