That's something I mentioned (I think) in the thread from the top five TV characters thread (the Barbara Walters thing a few months back) and something I added to 5 Ball - it kinda explains why Kermit is still reluctant to get married.
In the special, he did say he was waiting for basically everyone to be able to marry whom they wanted. At the time, I did kinda think that was a bit of a cope out (especially when he kinda grimaces/panics when asked), but when I wrote it in 5 Ball, it actually does make sense, depending on where you put them living.
See, my thought was, if they're living in California, neither couple could even be considered common law because the state doesn't recognize common law marriages and being interspecies as they are, the state might not take to them being officially married either, hence why they would probably
need to wait for same-sex marriages to pass.
That's probably getting a little too deep into it, but I tend to go way beyond the normal thought processes when writing fan fiction.