Is It Illegal to Marry a Third Cousin?

Is It Illegal to Marry a Third Cousin?


Albert Einstein married his cousin, Elsa Lowenthal, and we can probably all agree that he was a pretty smart fellow. So why is marrying a first cousin frowned upon in this country and outright barred in half of the states?

Some say that this is based on outdated notions that predate modern genetics and that the rules should be thrown out. Indeed, in many other countries marrying cousins is not considered at all problematic. In fact, about 20 percent of marriages, or one in five worldwide is between cousins, according to the Huffington Post. So let’s examine the myths and facts about cousin marriages.

Myth and Fact About Marriages Between Cousins

In short, yes, it is legal for second and third cousins to marry in the US. Beyong that, state laws get a little more complicated. According to the National Conference of State Legislatures:

“Twenty-five states prohibit marriages between first cousins. Six states allow first cousin marriage under certain circumstances, and North Carolina allows first cousin marriage but prohibits double-cousin marriage. States generally recognize marriages of first cousins married in a state where such marriages are legal.”

These prohibitions are thought to exist for reasons of genetics, which some say is based on a myth that has been debunked.

There is reportedly only a very slightly higher likelihood of genetic defects in children who are born of a cousin couple. The risk of birth defects in children born to first cousins is increased from a baseline of 3-4 percent to 4-7 percent, according to the National Society of Genetic Counselors.

With the genetic screening that exists today, that slightly higher risk rate could be mitigated. For example, pre-marital genetic testing could be mandated. But the National Society of Genetic Counselors reportedly does not consider this necessary and it does not recommend additional testing or screening for cousins.

It should be noted too that the risk of birth defects can rise for reasons other than familial closeness, like having children later in life or marrying into your own ethnicity. There are certain hereditary diseases that arise more frequently in particular ethnicities and are more likely to occur when two people of the same “tribe” marry — and this applies widely. For example, Ashkenazi Jews have an increased risk of children with Tay-Sachs disease when they intermarry, according to Huffington Post.

Taboos and Truths

The taboo against cousin marriages in this country is strong and some people say that this is to maintain the integrity of the gene pool and human intelligence. But the truth is that many of us are at least distant products of cousin marriages and many people we consider great minds married cousins in their time, including Johann Sebastian Bach, Edgar Allen Poe, and Charles Darwin.


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