I think you know where I'm going with this - can you date, or marry, someone that you are related to? Well, it begs the question, who are you related to? As humans, we are, of course, all related, whether you believe in Adam and Eve or Lucy. So when, exactly, are two people not related?
In terms of culture, anything beyond a first cousin is usually considered someone that you can safely have a blood test, and children, with. Your first cousins are the children of the siblings of your parents, so you probably know them anyway. And we humans have a pretty strong revulsion against incest.
Or, if you're not thinking of sex, you may be wondering how many Christmas cards you need to send out. Here the definition of "relatives" expands. 2nd cousins, cousins twice removed, etc. are considered by many people to be relatives worthy of a Christmas card. Personally, I don't send Christmas cards (with the perfect excuse of being an old bachelor), so it doesn't matter to me.
By the way, my Revolutionary War soldier was John Overstreet. If he is yours, too, send me an email and say, "hi cousin"!
Posted by Brad Hall