I have come to the conclusion that only about ten people on the entire Earth know what "third cousins, once removed" means. One of those ten people wrote a wikipedia article for the genalogically inept populace. Check it out, and then start sprinkling your conversation with terms like "zeroth cousin" for sibling and "negative first cousin" for grandparent. No wait, that doesn't make sense....dammit, maybe I should read that article again...
http://en.wikipedia.org/wiki/Cousin
Oh, and if you're wondering about the title,