# First cousins when a brother/sister marry another brother/sister **URL:** \ **Category:** Factual Questions\ **Created:** [April 13, 2013, 4:42am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572 "2013-04-13T04:42:39Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![Mississippienne](https://avatars.discourse-cdn.com/v4/letter/m/d2c977/32.png) [@Mississippienne](https://boards.straightdope.com/u/Mississippienne)\ **Post date:** [April 14, 2013, 1:50am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/21 "2013-04-14T01:50:15Z")
> [@septimus](#): > > One can find several marriages of double cousins in the Bourbon and Hapsburg pedigrees. > > For example, France’s King Louis XIII (son of King Henry IV and Maria de Medici, the famous Regent of France opposed by Richelieu) married Anne (daughter of Philip III (and II) King of Spain (and Portugal) and Margaret (both Hapsburgs). Meanwhile Louis XIII’s sister Elizabeth married Anne’s brother Philip IV (and III) King of Spain and Portugal. The Louis-Anne marriage produced Louis XIV the Sun-King. His first wife was Maria Theresia, the product of the Elizabeth-Philip marriage. The Habsburgs got freakishly inbred for awhile there, routinely marrying uncle to niece and double first cousins to each other. Part of it was a desire to keep certain lands in the family, and part of it was a lack of other Catholic dynasties of equivalent rank to marry with – so the Habsburgs tended to marry other Habsburgs. The notoriously inbred and pathetic Carlos II of Spain, physically and mentally deficient, is the most famous result of this, but astonishingly Carlos II had a full-sister, Margarita Teresa, who married their uncle and produced a surviving daughter of her own, Maria Antonia. Maria Antonia of Austria, the aforementioned niece of Carlos II, may be the most inbred European royal in recent-ish history of whom we have good documentation. Most people have 31 great-great-grandparents; Maria Antonia had only ten unique great-great-grandparents, and all of those ancestors were all closely related to one another. She was decended from her great-great-grandparents, Archduke Charles II of Austria and his wife Maria Anna of Bavaria (who were uncle and niece themselves), three times. Somewhat less famously, the Chinggisids (descendants of Genghis Khan) also tightly intermarried. Although the khans took many wives and concubines, their successors were almost always the sons of their chief wife, who was usually very closely related to them. They often married nieces and cousins, and even weirder, when a khan died his concubines would be inherited by his sons or brothers. This sometimes resulted in messes like that of Kokaji, a concubine to three Il-Khans of Persia in succession (Arghun, his brother Ghaykhatu, and Arghun’s son Ghazan) and had children by all three of them. Hulagu Khan’s daughter Todogach married Tanggis, khan of the Oirats, then after his death married Tanggis’ son Sulamish, and after his death married Sulamish’s son Chechak. So she was married to grandfather, son, and grandson. It gets weirder. Todogach and Sulamish had a daughter, Oljatai, who married Arghun, Il-Khan of Persia (who’s father, Abaka, was a son of Hulagu). Another of Arghun’s wives was Kutlug, daughter of Tanggis by his other wife, a daughter of Guyuk Khan (himself son of Ogodei). Kutlug was the mother of Ghazan, Il-Khan of Persia. Hulagu and Guyuk’s fathers, Tolui and Ogodei respectively, were brothers and sons of Genghis Khan. Is your head spinning yet? ---
**Author:** ![Batfish](https://avatars.discourse-cdn.com/v4/letter/b/a3d4f5/32.png) [@Batfish](https://boards.straightdope.com/u/Batfish)\ **Post date:** [April 14, 2013, 2:50pm UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/22 "2013-04-14T14:50:41Z")
You know, this really wasn’t a thread about inbreeding. ---
**Author:** ![Fair\_Rarity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fair_rarity/32/153_2.png) [@Fair\_Rarity](https://boards.straightdope.com/u/Fair_Rarity)\ **Post date:** [April 15, 2013, 2:07am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/23 "2013-04-15T02:07:43Z")
I have triple first cousins in my family. Three brothers married three sisters. Made it very confusing for me as a child trying to figure out why all the adults had the same last name after marriage. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [April 15, 2013, 4:07am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/24 "2013-04-15T04:07:53Z")
> [@John\_Mace](#): > > We may have found the elusive “gay gene”! 😉 There are 23 in my generation. Two of us are out, and I have suspicions of two more. one of whom has kids. The “bad gene” is only on my father’s side of the family. I think some of them are asexual. ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [April 15, 2013, 8:32am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/25 "2013-04-15T08:32:04Z")
> [@Fair\_Rarity](#): > > I have triple first cousins in my family. Three brothers married three sisters. Made it very confusing for me as a child trying to figure out why all the adults had the same last name after marriage. Sorry to be the perennial nitpicker, but I don’t think this is properly called “triple cousins.” Any pair from the three marriages will be “double cousins” because they share four of four grandparents … but sharing more than four is impossible! There’s an odd situation involving my neighbors, which also isn’t “triple cousins” though it seems it should have a name like that: Two brothers married two unrelated women. One of the wives has a brother who married the sister of the other wife. (Note that there’s no inbreeding involved.) All three couples are our neighbors; in fact I just shared a beer with the man whose sister’s brother-in-law is married to this man’s sister-in-law. ---
**Author:** ![Annie-Xmas](https://avatars.discourse-cdn.com/v4/letter/a/ecc23a/32.png) [@Annie-Xmas](https://boards.straightdope.com/u/Annie-Xmas)\ **Post date:** [April 15, 2013, 2:15pm UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/27 "2013-04-15T14:15:42Z")
Laura Ingalls Wilder had two sets of double first cousins–her father’s brother married her mother’s sister and vice versa. Fred & Martha Gilbreth, of Cheaper by the Dozen fame, married a sister and brother, Jessie & Richard Tallman. ---
**Author:** ![Dr.Drake](https://avatars.discourse-cdn.com/v4/letter/d/ad7895/32.png) [@Dr.Drake](https://boards.straightdope.com/u/Dr.Drake)\ **Post date:** [April 15, 2013, 3:05pm UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/28 "2013-04-15T15:05:10Z")
> [@septimus](#): > > Sorry to be the perennial nitpicker, but I don’t think this is properly called “triple cousins.” Any pair from the three marriages will be “double cousins” because they share four of four grandparents … but sharing more than four is impossible! > > There’s an odd situation involving my neighbors, which also isn’t “triple cousins” though it seems it should have a name like that: > > Two brothers married two unrelated women. One of the wives has a brother who married the sister of the other wife. (Note that there’s no inbreeding involved.) All three couples are our neighbors; in fact I just shared a beer with the man whose sister’s brother-in-law is married to this man’s sister-in-law. This happened in my family, too. My grandfather’s brother married my grandmother’s sister. That grandfather’s sister and another one of my grandmother’s sisters married a pair of brothers. ---
**Author:** ![Jman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jman/32/4416_2.png) [@Jman](https://boards.straightdope.com/u/Jman)\ **Post date:** [April 15, 2013, 3:20pm UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/29 "2013-04-15T15:20:18Z")
> [@Mississippienne](#): > > Double first cousins have a coefficient of relationship of 1/4th – equivalent to being uncle/niece or half-brother/half-sister. Siblings have a relationship of 1/4…uncle/neice is 1/8, and I’m assuming double cousins are 1/8 as well. Regular first cousins share 1/16 of their DNA. ---
**Author:** ![Fair\_Rarity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fair_rarity/32/153_2.png) [@Fair\_Rarity](https://boards.straightdope.com/u/Fair_Rarity)\ **Post date:** [April 16, 2013, 1:17am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/30 "2013-04-16T01:17:41Z")
> [@septimus](#): > > Sorry to be the perennial nitpicker, but I don’t think this is properly called “triple cousins.” Any pair from the three marriages will be “double cousins” because they share four of four grandparents … but sharing more than four is impossible! I use the term not in a genetic sense, but in a humorous way to say my great-grandparents really liked each other’s families a lot… or there weren’t a lot of other eligible single people in their town. 😉 ---
**Author:** ![maggenpye](https://avatars.discourse-cdn.com/v4/letter/m/ecc23a/32.png) [@maggenpye](https://boards.straightdope.com/u/maggenpye)\ **Post date:** [April 16, 2013, 1:25am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/31 "2013-04-16T01:25:08Z")
> [@Fair\_Rarity](#): > > I use the term not in a genetic sense, but in a humorous way to say my great-grandparents really liked each other’s families a lot… or there weren’t a lot of other eligible single people in their town. 😉 We have a similar joke in my family where one set of twins married another set of twins - we’re all very relieved the various offspring moved to different countries before finding mates. 😃 ---
**Author:** ![FuzzyOgre](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@FuzzyOgre](https://boards.straightdope.com/u/FuzzyOgre)\ **Post date:** [April 16, 2013, 2:00am UTC](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572/32 "2013-04-16T02:00:24Z")
My dad has 12 double first cousins. The wives of his father and uncle are sisters. Both couples had 12 children. No miscarriages either. So I have 12 double first cousins once removed(if I understand how it works), 24 first cousins, and probably ~24 double second cousins, and since they are all having kids too, 50 more cousins of some sort from them. My first cousins have a bunch of kids too. It gets confusing. [Previous page](https://boards.straightdope.com/t/first-cousins-when-a-brother-sister-marry-another-brother-sister/655572.md?page=1)