A lot of people here are missing the point. I am very religious and I support Gay marriage in the United States. I support this because I believe that they are not really married in God's eyes. They do not receive the HOLY MATRIMONY that God gives you when you are married in the Church. LEGALLY nowhere in the Constitution or any Federal law does it say that Marriage is between a man and a woman. In fact the Constitution says "All men are created EQUAL"
There is a huge difference between Holy Matrimony and Marriage. Marriage is just a legal term and a tax write-off. Who cares who is legally "together" by not letting them marry, you are just going to make them get louder and more obnoxious than they are now and they are not going to stop fucking each other just because they cannot get married. Who gives a fukc if they have a paper that says they are legal. Let them suffer like the rest of us.
Now on the other hand you can see how people who want to marry children will step up or Steveo will want to marry his favorite sheep. There needs to be clear distinctions in the law. MY idea would be:
Any adult above the age of 18 can marry any other adult above the age of 18
Any person wishing to marry below the age of 18 may do so if and only if they are above the age of 16 and have consent of their parents or legal guardians.