Yeah I understand the pity party thing. I invite you to consider that at least a part of this is how you view yourself within the family. But hey, who am I to advise? I know for a fact I play the scapegoat. I'm the mirror that no one wants to look in. I will always be the baby, the nut job, the drunk, crazy, and FEMALE. No matter what I do, that will never change. AND the biggest part of it is ME. I can't seem to change my behavior in relation to them. I have pigeon holed myself as much, or more really, than they do. And I know for a fact that they don't think about any of 'this', or me for that matter, as much as I do. I am quite sure that each child in my large family has experienced the 'family' differently depending on their role. Even our memories of the same events are different (and of course mine are wrong...haha)...it is very interesting.
So all I can do is stay away. Its survival. I moved far away so I wouldn't have to deal with exactly what you discuss....the invites, the calls. Now my family isn't anywhere near as 'connected' as yours appears to be. But I missed an awful lot because of all this....and I regret some of that. But really, there was no choice at the time and there still isn't.
You can choose to distance if you want. You just have to decide for yourself who you are, what you are, and how you feel about yourself. You have to write your own narrative and stop letting the fam write it for you. Its really hard.