Here Is The Surprising Truth About Cousins And Marriage

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Albert Einstein married his cousin, and he’s a genius.

According to overlooked research into the practice of consanguineous marriage, or the marital union of kin, that genius may have been onto something.

Los Angeles Times Archive

The prevailing taboo against kissing this relative is so strong that we have a term—”kissing cousins“—which we use as a pejorative. But is it really such a bad thing to marry your cousin?

Not according to genetic counselor Robin Bennett, who was president of the National Society of Genetic Counselors back in 2002. That year, Bennett and her organization conducted a major literature review of six important scientific studies on the risk of birth defects in children whose parents are cousins.

When first cousins marry and bear children, “there is a slightly increased risk, but in terms of general risks in life it’s not very high,” Arno Motulsky, professor of medicine and genome sciences at the University of Washington, told The New York Times when news of the misconception broke.

Arno Motulsky/Clare McLean

According to the studies, which were conducted between 1965 and 2000 and looked at thousands of births, the risk of serious birth defects in the children of consanguineous parents does rise—but only from 3 to 4 percent. For first cousins, the risk goes up by 1.7 to 2.8 percentage points, potentially doubling the chance that a child will be born with spina bifida or another life-threatening condition.

That sounds bad, but the researchers point out that the original risk is so small that even doubling it hardly warrants the social taboos and legal bans that discourage cousins from marrying. In fact, women face the same increased risk when they have children at age 40  instead of age 30; however, no one rallies for the restriction of childbirth after the mother turns 30.


Considering the risk of children of cousins is so much lower than people tend to assume, it’s fair to ask why 31 states in the U.S. still have laws banning these marriages.

So, where did all these bans on cousin marriage come from, anyway?

In the Western world, the laws against cousins marrying started with the Catholic Church. Canon law forbade marriages between first and second cousins beginning with the Council of Agde in 506 A.D. In the 1,500 years since, the Church has softened its stance; today, Catholic second cousins can marry just like anyone else, and first cousins can get hitched with a special dispensation.

Edward Peters

In the United States, the government didn’t really get involved in the issue until after the Civil War. Following the four bloody years of conflict, states started to exert more control over citizens, passing legislation that affected education and citizen health. As part of that broader movement, lots of states enacted their bans against consanguineous marriage. Many of those laws remain, because honestly, what politician wants to make cousins’ right to marry a plank in their platform?

Meanwhile, many other cultures are totally fine with even first cousins marrying. In primarily Islamic countries, somewhere between 20 and 50 percent of all marriages are consanguineous. In a 2000 paper published in Ethnology, a journal founded by George P. Murdock, researcher A. Korotayev writes that “the overwhelming majority of cross-cousin marriages appear among the Islamic cultures of North Africa, and those of West and Central Asia.”

Public Domain

Cultures that allow cousins to marry are just carrying on a tradition that’s as old as humanity itself. According to Robin Fox, an anthropology professor at Rutgers University, some 80 percent of all marriages in human history have been between cousins.

There appears to be growing resistance to the taboo.

Today, cousins fall in love just like any other relationship. Many of these couples wish to marry, and now there are resources to help them out. describes itself as “the world’s primary resource for romantic relationships among cousins.” On that site, “kissing cousins” can gather to organize resistance to the laws that forbid them to marry.


The activist writers of this site have a theory as to why the taboo against cousin marriage still exists more than 15 years after the National Society of Genetic Counselors argued that risks to children didn’t justify the public distaste.

“Why shouldn’t cousins be allowed to marry?” asks the site.


Opponents of cousin marriage generally cite the Bible or genetic birth defects. As previously mentioned, the Bible supports cousin marriages and the risks of having offspring within a cousin marriage are similar to having a child later in life, which is not, of course, illegal.

This suggests that marriage restrictions against cousins are based only on the somewhat faulty presuppositions and prejudice.


The New York Times talked to married cousins named Kathy and Dale Hollenbach in 2009. Kathy made an appeal that would have been familiar to the Einsteins.

“What I tell everyone is that you don’t choose who you fall in love with,” she said. “You can deny your feelings, but that leads to being a miserable person who goes through life trying to find a partner just like your cousin. Which will never happen.”

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