I've got similar deal going with my closest, oldest (20 year +) friends lost due to some horrid marriage.
Closest friends? I see a trend here and from the OP. Think about whether you are actually the problem?
Maybe they grew up and don't hang out, play poker or play beer pong anymore? When you're married, you can't hang out as much. You can't crash at their house anymore. You don't golf with your buddies twice in one day.
It's a given. You aren't a true friend for cutting them off just because they are married or going to a rough patch. Marriage is a commitment to your spouse not to your former drinking buddies. Sorry, has to be said.