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What's a Second Cousin vs. a First Cousin Once-Removed?

If you can't keep your third cousins and your first cousins twice removed straight, you are not alone. But there's a simple way to figure out the relationships between relations.

First cousins share a grandparent, second cousins share a great-grandparent, third cousins share a great-great-grandparent, and so on. The degree of cousinhood ("first," "second," etc.) denotes the number of generations between two cousins and their nearest common ancestor.

The term "removed" refers to the number of generations separating the cousins themselves. So your first cousin once removed is the child (or parent) of your first cousin. Your second cousin once removed is the child (or parent) of your second cousin. And your first cousin twice removed is the grandchild (or grandparent) of your first cousin.

Clearly, it doesn't take many generations before your family tree is a bit unwieldy. Case in point: In 2007, it was revealed that vice president Dick Cheney and presidential hopeful Barack Obama are eighth cousins. Cheney's wife, Lynn Cheney, discovered this tidbit while researching her husband's genealogy for a memoir she was writing, the Associated Press reported.

If these distinctions aren't confusing enough, first cousins can be further parsed into parallel and cross cousins. Parallel cousins are the children of same-sex siblings — for example, the children of your mother's sister are your parallel cousins. Cross cousins are the offspring of opposite sex siblings, such as your mother's brother's children, or your father's sister's children.

And in case you were wondering, the two relatives at the family reunion (A's mother's aunt is B's father's grandmother) are second cousins once removed.

Originally published on Live Science.