It's a legal basis for justifying incestuous marriages.
If you base incest in the classical, traditional way, but soon it will have to be redefined as is being done with marriage.
Seems to me, when you strip away everything from a civil marriage, you must.....
Love: the government can't mandate, nor test for love
Sex: the government can't mandate sexual intimacy
Faithfulness: a traditional value that the government can't mandate.
So marriage is simply a new financial tool open to 10's of millions for lower taxes and better employer benefits.
I find it funny that gays think this is about them, when there are far more straight same sex couples that can/will seek a $50.00 marriage license to save a pot load of money.
Marriage simply becomes an IRA or 401k, and the couple ....an LLC or S corp.
Hell, gays could possibly be a small minority of same sex marriage.
Why should same sex siblings be denied the right to marry SIMPLY BECAUSE THEY WERE BORN THAT WAY.