I've sat on the sidelines of similar gigs with my own family. I was married to a Catholic girl, and these things seemed common place. I initially felt left out from may situations, like you are now - even with my own sisters. And each event was cackled about, poured over, and even made un-realistic from the female's side. I just watched the comedy, and shook my head. When they finally approached me over time (as I rarely was stressed over ANY family problems/plans or parties they caused or bickered over). I'd just grin, and tell them they are doing fine.