# Why is cousin marriage prohibited in some US states? **URL:** \ **Category:** Factual Questions\ **Created:** [September 2, 2014, 12:01am UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205 "2014-09-02T00:01:36Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![Bert\_Nobbins](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@Bert\_Nobbins](https://boards.straightdope.com/u/Bert_Nobbins)\ **Post date:** [September 2, 2014, 4:24pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/21 "2014-09-02T16:24:36Z")
> [@LSLGuy](#): > > At least here (US) & now, “sister-in-law” means either the sibling of a spouse or the spouse of a sibling. Neither of which is somebody related by blood to the person the rules are addressing. The sister-in-law business caused much controversy in Victorian England, not sorted out until 1907. [http://en.wikipedia.org/wiki/Deceased\_Wife%27s\_Sister%27s\_Marriage\_Act\_1907](http://en.wikipedia.org/wiki/Deceased_Wife%27s_Sister%27s_Marriage_Act_1907) ---
**Author:** ![robert\_columbia](https://avatars.discourse-cdn.com/v4/letter/r/e79b87/32.png) [@robert\_columbia](https://boards.straightdope.com/u/robert_columbia)\ **Post date:** [September 2, 2014, 4:36pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/22 "2014-09-02T16:36:09Z")
> [@Claverhouse](#): > > …**[Rhode Island permits](http://lists.ucla.edu/pipermail/religionlaw/2013-October/026767.html)** it from 1764 on, but only for those of the jewish faith… It would be interesting to consider how Rhode Island officially defines Jewish people. E.g. does it apply the typical Orthodox Jewish rules or does it use self-identification as Jewish? What happens if there are two synagogues in town and one says that you are Jewish and one says that you are not? Would a family court actually consult the Talmud and try to interpret Jewish law? What happens if you are clearly considered Jewish under Jewish law but you are an atheist? What if you are a Christian believer? Muslim? Buddhist? ---
**Author:** ![mbh](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@mbh](https://boards.straightdope.com/u/mbh)\ **Post date:** [September 2, 2014, 4:56pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/23 "2014-09-02T16:56:57Z")
> **[Consanguinity](https://en.wikipedia.org/wiki/Consanguinity)** > > Consanguinity (from Latin consanguinitas 'blood relationship') is the characteristic of having a kinship with a relative who is descended from a common ancestor. > Many jurisdictions have laws prohibiting people who are closely related by blood from marrying or having sexual relations with each other. The degree of consanguinity that gives rise to this prohibition varies from place to place. On the other hand, around 20% of the global population lives in areas where some consanguinous marriages ar... > [@](#): > > Under Roman civil law, which early canon law of the Catholic Church followed, couples were forbidden to marry if they were within four degrees of consanguinity.[5] In the ninth century the church raised the number of prohibited degrees to seven and changed the method by which they were calculated.[6] Eventually the nobility became too interrelated to marry as the pool of non-related prospective spouses became smaller. It was either defy the church’s position or look elsewhere for eligible marriage candidates.[7] In 1215 the Fourth Lateran Council made what they believed was a necessary change to canon law reducing the number of prohibited degrees of consanguinity from seven back to four.[8] The method of calculating prohibited degrees was changed also.[9] Instead of the former practice of counting up to the common ancestor then down to the proposed spouse, the new law computed consanguinity by counting back to the common ancestor.[9] In the Roman Catholic Church, unknowingly marrying a closely consanguineous blood relative was grounds for an annulment, but during the eleventh and twelfth centuries dispensations were granted with increasing frequency due to the thousands of persons encompassed in the prohibition at seven degrees and the hardships this posed for finding potential spouses.[10] After 1215 the general rule was that while fourth cousins could marry without dispensation, generally the need for dispensations was greatly reduced.[10] In fourteenth century England, for example, papal dispensations for annulments due to consanguinity (and affinity) were relatively few.[11] > **[Cousin marriage](https://en.wikipedia.org/wiki/Cousin_marriage)** > > A cousin marriage is a marriage where the spouses are cousins (i.e. people with common grandparents or people who share other fairly recent ancestors). The practice was common in earlier times and continues to be common in some societies today, though in some jurisdictions such marriages are prohibited. Worldwide, more than 10% of marriages are between first or second cousins. Cousin marriage is an important topic in anthropology and alliance theory. > In some cultures and communities, cousin m... > [@](#): > > Cousin marriage was legal in all states before the Civil War.[citation needed] However, according to Kansas anthropology professor Martin Ottenheimer,[19] the main purposes of marriage prohibitions were maintaining the social order and upholding religious morality and safeguarding the creation of fit offspring. Indeed, writers such as Noah Webster (1758–1843) and ministers like Philip Milledoler (1775–1852) and Joshua McIlvaine helped lay the groundwork for such viewpoints well before 1860. This led to a gradual shift in concern from affinal unions, like those between a man and his deceased wife’s sister, to consanguineous unions. By the 1870s, Lewis Henry Morgan (1818–1881) was writing about “the advantages of marriages between unrelated persons” and the necessity of avoiding “the evils of consanguine marriage”, avoidance of which would “increase the vigor of the stock”. To many, Morgan included, cousin marriage, and more specifically parallel-cousin marriage, was a remnant of a more primitive stage of human social organization.[20] Morgan himself had married his maternal uncle’s daughter in 1851.[21] > > In 1846 Massachusetts Governor George N. Briggs appointed a commission to study “idiots” in the state, and this implicated cousin marriage as responsible for idiocy. Within the next two decades numerous reports, e.g., one from the Kentucky Deaf and Dumb Asylum, appeared with similar conclusions: that cousin marriage sometimes resulted in deafness, blindness, and idiocy. Perhaps most important was the report of physician Samuel Merrifield Bemiss for the American Medical Association, which concluded “that multiplication of the same blood by in-and-in marrying does incontestably lead in the aggregate to the physical and mental depravation of the offspring”. Despite being contradicted by other studies like those of George Darwin and Alan Huth in England and Robert Newman in New York, the report’s conclusions were widely accepted.[22] > > These developments led to 13 states and territories passing cousin marriage prohibitions by the 1880s. Though contemporaneous, the eugenics movement did not play much of a direct role in the bans, and indeed George Louis Arner in 1908 considered the ban a clumsy and ineffective method of eugenics, which he thought would eventually be replaced by more refined techniques. Ottenheimer considers both the bans and eugenics to be “one of several reactions to the fear that American society might degenerate”.[23] In any case, by the period up until the mid-1920s the number of bans had more than doubled.[7] Since that time, the only three states to add this prohibition have been Kentucky in 1943, Maine in 1985, and Texas in 2005. The NCCUSL unanimously recommended in 1970 that all such laws should be repealed, but no state has dropped its prohibition since the mid-1920s.[1][9][24] ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [September 7, 2014, 5:01pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/24 "2014-09-07T17:01:52Z")
> [@Yllaria](#): > > The only instance I can think of off hand is the Onan story. In that case, the brother had died before having a son who could inherit his property - property that included his wife, the hypothetical son’s mother. HS would have been expected to assume the care and feeding of his mother through her old age. Presumably, she would like that better than being a shirt-tail addition to a more distant relative’s family. > > Onan was not supposed to marry his sister-in-law, he was supposed to get her pregnant. If he did that quickly, the child would then be his brother’s son and inherit his brother’s property. Onan was, unfortunately, ambivalent about that. It’s part of being a “kinsman redeemer,” and it was important in Ruth, too. In that story, we find that it goes from most related on out, and that you can opt out. To be more specific, it is [Yibbum](http://en.wikipedia.org/wiki/Yibbum) or [levirite marriage](http://en.wikipedia.org/wiki/Levirate_marriage). And there is a way out of the obligation that is strongly encouraged by most Jewish communities. As you stated, it only applies if there are no male descendents, and was a way to preserve the bothers lineage. But it also entitled the brother to his property, as well. ---
**Author:** ![RivkahChaya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rivkahchaya/32/8919_2.png) [@RivkahChaya](https://boards.straightdope.com/u/RivkahChaya)\ **Post date:** [September 7, 2014, 5:15pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/25 "2014-09-07T17:15:52Z")
> [@Chronos](#): > > On the other hand, doesn’t Judaism actually _require_ sibling-in-law marriage in some cases? No. It was apparently something practiced by some of the people who became the Israelites/Jews, what have you, but by the time any law was recorded in the Torah, the practice was in disfavor, and there was already a ritual by which a person could get out of the obligation, which someone was supposed to do instead of getting his sister-in-law pregnant. There are traditions of at least two groups, which are reconciled as best as possible in the Torah. One group had at one time had the practice of a brother getting a sister-in-law pregnant, if his brother died without issue, but at least one other group had a tradition that such couplings were forbidden. ---
**Author:** ![tapu](https://avatars.discourse-cdn.com/v4/letter/t/49beb7/32.png) [@tapu](https://boards.straightdope.com/u/tapu)\ **Post date:** [September 7, 2014, 5:38pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/26 "2014-09-07T17:38:24Z")
Even sib-sib marriage isn’t as big a risk as many think. And when you get to first cousins, it’s negligible. What’s dangerous is inter-marriage across several successive generations. The “Royal Problem.” That said, it is odd to me, too, that so many states bar first-cousin marriage. Here’s an anecdote that furthers the intrigue, I think: My birthplace, in the OH-WV-KY triangle, has a long history of being denigrated for culture and lifestyle, including dialect, clothing, lack of mandatory education, and–intermarriage. We are the people of Hee Haw, the families of Beverly Hillbillies. What’s pertinent to the OP is that we make the biggest f’ing deals out of tracing our family trees to ensure no cousin marries their cousin. We get together with big genetic charts at our reunions (attendance: 100s) and look into what young’un is fancying another. I remember, as a teenager, that they made me stop seeing George–he was determined to be my 2nd cousin, once removed, or somesuch. No discussion–George and I just went, “Aw shucks.” Now, I think that the matter is treated as such a taboo for two reasons: That area of upper Appalachia was isolated and contained just so many families for a century or more, so having come from England, Scotland, Ireland, we avoided intermarriaage as a remnant of that Royal Problem. And then second, the stigma was so established. The movie “Deliverance” didn’t start the idea that the area was inbred–it just made it extremely widely known. But the movie producers were playing off a long-held belief (not nec false, just exaggerated) that intermaarriage in that part of the country was common, successive, and bore dire consequences–namely, reduced intellect in offspring. ---
**Author:** ![Mr.Excellent](https://avatars.discourse-cdn.com/v4/letter/m/f19dbf/32.png) [@Mr.Excellent](https://boards.straightdope.com/u/Mr.Excellent)\ **Post date:** [September 7, 2014, 6:58pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/27 "2014-09-07T18:58:03Z")
> [@Great\_Antibob](#): > > [Sure it is](http://en.wikipedia.org/wiki/Cousin_marriage#Biological_aspects). > > That said, it’s an increased risk and not an outright guarantee of birth defects, but there is a valid biological rationale that can be considered. I stand corrected - thank you! ---
**Author:** ![BrotherCadfael](https://avatars.discourse-cdn.com/v4/letter/b/977dab/32.png) [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)\ **Post date:** [September 7, 2014, 7:25pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/28 "2014-09-07T19:25:06Z")
> [@Claverhouse](#): > > However, _wanting_ to marry a niece ( or an uncle ) must be pretty rare. I would think it most likely when you have an uncle-niece pairing of similar age - they would think of themselves more like cousins than their actual relationship. ---
**Author:** ![Guinastasia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guinastasia/32/5751_2.png) [@Guinastasia](https://boards.straightdope.com/u/Guinastasia)\ **Post date:** [September 7, 2014, 7:46pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/29 "2014-09-07T19:46:52Z")
> [@tapu](#): > > Even sib-sib marriage isn’t as big a risk as many think. And when you get to first cousins, it’s negligible. What’s dangerous is inter-marriage across several successive generations. The “Royal Problem.” [THAT’S](http://en.wikipedia.org/wiki/Charles_II_of_Spain) putting it mildly. 😉 (Contrary to popular belief, hemophilia in the royal families was NOT caused by inbreeding – however, because Queen Victoria had such a large family, and royalty only married royalty, it ended up spreading into other royal families, and causing such a huge problem.) ---
**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:** [September 7, 2014, 8:32pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/30 "2014-09-07T20:32:00Z")
> [@Great\_Antibob](#): > > [Sure it is](http://en.wikipedia.org/wiki/Cousin_marriage#Biological_aspects). > > That said, it’s an increased risk and not an outright guarantee of birth defects, but there is a valid biological rationale that can be considered. **Great Antibob** ’s link implies that cousin marriage is, very roughly, near the threshold for serious inbreeding risk: > [@](#): > > Put differently, first-cousin marriage entails a similar increased risk of birth defects and mortality as a woman faces when she gives birth at age 41 rather than at 30. Critics argue that banning first-cousin marriages would make as much sense as trying to ban childbearing by older women. But that’s assuming the cousin relationship is the _only_ genetic kinship. If instead you’re dealing with cousins marrying whose parents were themselves already slightly inbred, you get cases like (as the same page points out): > [@](#): > > For example, because the entire Amish population is descended from only a few hundred 18th-century German-Swiss settlers, the average coefficient of inbreeding between two random Amish is higher than between two non-Amish second cousins. First-cousin marriage is taboo among Amish but they still suffer from several rare genetic disorders. Eyeballing [the states which prohibit cousin marriages](https://en.wikipedia.org/wiki/Cousin_marriage_law_in_the_United_States_by_state), the prohibitions tend to be in Mormon country or Appalachia, where inbreeding is already higher than normal. ---
**Author:** ![Rick\_Kitchen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rick_kitchen/32/522_2.png) [@Rick\_Kitchen](https://boards.straightdope.com/u/Rick_Kitchen)\ **Post date:** [September 7, 2014, 9:43pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/31 "2014-09-07T21:43:25Z")
My grandmother’s sister married their first cousin. Their parents were first cousins. _Their_ parents were first cousins. _Their_ parents were something like second cousins, or once-removeds, or something like that. My grandmother’s sister was married in Oklahoma, but the other marriages were in Tennessee. It was a very remote community. And hey, I came out okay. Just ask me! ---
**Author:** ![tapu](https://avatars.discourse-cdn.com/v4/letter/t/49beb7/32.png) [@tapu](https://boards.straightdope.com/u/tapu)\ **Post date:** [September 7, 2014, 10:42pm UTC](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205/32 "2014-09-07T22:42:40Z")
> [@Guinastasia](#): > > [THAT’S](http://en.wikipedia.org/wiki/Charles_II_of_Spain) putting it mildly. 😉 > > (Contrary to popular belief, hemophilia in the royal families was NOT caused by inbreeding – however, because Queen Victoria had such a large family, and royalty only married royalty, it ended up spreading into other royal families, and causing such a huge problem.) Plus, the ugliness. 😉 [Previous page](https://boards.straightdope.com/t/why-is-cousin-marriage-prohibited-in-some-us-states/697205.md?page=1)