Your Ancestors Might have Married their Cousins

There was a time when it was considered normal (perhaps even preferable) for a person to marry his or her cousin. Over time, it became less socially acceptable to view one’s cousins as a potential spouse. It is possible that one of your ancestors married his or her cousin.

Before the Industrial Revolution, people tended to live near their relatives. When people were ready to find a spouse, they looked at those who lived near them. As such, it was not uncommon for a person to end up married to his or her cousin.

Thomas Jefferson married Martha Wayles Skelton on January 1, 1772. Martha and Thomas were third cousins and married after Martha became a young widow. Thomas and Martha had six children, but only two survived into adulthood. Martha died at age 33 following complications from child-birth.

Researchers put together a 13 million person family tree that was created by compiling and validating 86 million public profiles from One thing that the researchers learned from the data was that the advent of mass railroad travel between 1825 and 1875 did not cause people to avoid marrying their cousins. It turns out that genetic relatedness of many couples increased over that time period.

Geographic mobility was not the biggest factor in causing people to stop marrying their cousins. The bigger reason was that social norms regarding cousin marriage changed. After 1875, married partners started to become less and less related.

Prohibitions on cousin marriage date to the Civil War in the United States. The first ban was enacted by Kansas in 1858, followed by Nevada, North Dakota, South Dakota, Washington, New Hampshire, Ohio, and Wyoming in the 1860s. The increase in the rate of marriage ban laws was nearly constant until the mid-1920s.

Franklin Delano Roosevelt was fifth cousins with Theodore Roosevelt (who was elected President in 1900). When Franklin was in college, he fell in love with Theodore’s niece, Anna Eleanor Roosevelt.

The two first met when they were children, and were reacquainted at a White House dinner in 1902. Franklin and Eleanor were married on St. Patrick’s Day in 1905 and had six children in a span of 10 years. Franklin and Eleanor were distant cousins.

Today, the following states allow first cousins to marry each other: Alabama, Alaska, California, Colorado, Connecticut, District of Columbia, Florida, Georgia, Hawaii, Maryland, Massachusetts, New Jersey, New Mexico, New York, Rhode Island, South Carolina, Tennessee, Vermont, and Virginia. Other states have restrictions placed that determine whether or not first cousins can marry.

Related Articles at

* A Brief History of Cousins Marrying Cousins

* Researchers Built a 13 Million Person Family Tree

* A Brief History of Marriage Laws in the United States

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