In a perfect world, the right to a civil union would be extended to both straight and gay people and marriage would remain a purely religious institution that isn't state-sanctioned. In this world, pro-gay marriage.
Care to elaborate?
Does that also count for siblings and people living in polygamous relationships? "Marriage Equality", by definition of the term, obviously involves much more than gay and lesbian couples.
I don't see why marriage between multiple people and/or people who are related should be prohibited though polygamy would probably be harder to deal with, practically speaking.