Well then why not marry children? Whose to say that a 17 year old is so much less advanced than an 18 year old. For that matter, a 21 year old vs an 18 year old. Its all arbitrary. Homosexual marriage is legal in what states deem in legal, and that's that. Other states have more sense, and therefore continue traditional (shall I say, biological) marriage. Last time I checked, two men cannot make a child.