I'm in the same situation with my best friend and his boyfriend (yes, they are gay). I have managed to help them with their relationship a few times, I think it's because I'm entirely logical about relationship stuff while for most people there are a bunch of strong emotions involved or something like that. But yeah, I've launghed at that too because I have no relationship experience and this is my friend's third relationship so you'd think that I am the last person he would ask for relationship advise.