I wonder this too. Since gays (particularly men) have had to create their own version of what a relationship looks like, open relationships are often the norm. Maybe "often" isn't the right word, but the frequency of it is WAY higher than in hetero relationships. That makes might make for a higher success rate with marriages.
I'm guessing if men had the blessings of their wives to go fuck a slut every once in a while more marriages would stay together.
I support this theory. My parents divorced because my dad is a fucking player, and I'm sure a few of my aunts\uncles had the same problem, too.
I think most of the gay couples I know are in an open relationship; when I had a boyfriend, I was the only one I knew who was monogamous (thank goodness that's done for). I think even the couple with a kid weren't exclusive with each other.
Now, only one of the guys I "don't have sex" with (I don't fuck, I'm asexual) is actually in a relationship; the other 9 or so are free agents, and two of them identify as 'strictly monogamous' (yet, they're still okay with sexy time with me, LOL).
Pretty psyched on the whole equal marriage thing, even though I have no desire for it.
Hope it really helps kids be more comfortable with themselves.
Now, there's s shit ton of more work to do...