A number of people ask me that question after reading my page about cousins, which explains first cousins twice removed and second cousins once removed.
Short answer: sure, unless your family has a history of genetic problems.
In 26 out of 50 states in the United States, and many other countries, first cousins can marry. Second cousins, third cousins, first cousins once removed, and any other cousins except first cousins can marry in all 50 states and every country in the world.The Roman Catholic Church, which has had much more experience with people than the Unites States has, being bigger and older, frowns on it. You must seek a dispensation from your Bishop to marry your first cousin.
It used to be common. Where my ancestors came from, Monroe County Virginia (now West Virginia), before 1850 if people wanted to marry someone who wasn't an Indian, they had a choice of a cousin or nothing; it was sparsely populated. A lot of my Monroe County relatives married first cousins. Even more married a bit further "out" - second, first once removed, third, etc.
If you do genealogy, and your ancestors were in the USA west of the Atlantic seaboard before the Civil War, odds are you'll find at least one set of first cousins marrying in your tree. It is easy to see why if you do a little math.
There was a brief span of time in the US (1870 - 1930 or so), after doctors started washing their hands and before birth control was popular, when women routinely had 8 - 12 children, most of whom lived to adulthood. If that happened two generations in a row, one couple could have 8 - 12 children who married and produced 8 - 12 children in turn, giving the original couple 64 - 144 grandchildren. Just to make my example easy, say the couple had 10 children who had 10 children each, for 100 grandchildren. That means each grandchild would have 9 siblings, 90 first cousins on their father's side and 90 first cousins on their mother's side.
If you take it up a notch, to three generations, each great-grandchild could have 900 second cousins on each side of their family. Second cousins share great-grandparents, not grandparents. You have four sets of great-grandparents, and (4 x 900) makes 3,600 second cousins in addition to the 180 first cousins. In a sparsely-populated county you'd have to look a long ways to marry someone who wasn't related to you.
I'm not an expert on personal relations; if I were, my teenagers would listen when I gave advice. You should seek other opinions if you get serious about a cousin. Use the two words:
in any reputable search engine and you'll find lots of
discussion on the topic.
Cousin Couples seemed to be the most elaborate to me, in a cursory glance.
You might want to talk with your rabbi, minister or priest, too.
On the bright side, the most stable marriages (dull, but stable) are between people from similar geographic, religious, social, economic and racial backgrounds. Cousins usually have somewhat similar backgrounds. Their backgrounds are a lot closer than if, for instance, one of you is a poor Norwegian Lutheran and the other is a rich Chinese Buddhist. Diverse backgrounds don't mean a sure divorce. I'll bet somewhere in Hawaii right now there are people celebrating their golden wedding anniversary with sweet and sour lutefisk.
On the dim side, if hemophilia, Huntington's Chorea or any other genetic problems run in your family, you'd be foolish to marry a cousin. It would be like playing Russian Roulette with bullets in five of the six chambers.
This is part of the Genealogy section of my web site, but most people who use it just want to date their cousin, not trace their family tree, so I don't have the Genealogy navigation bar on this page. Feel free to look around via the navigation bar below: