(sorry for another wedding dilemma thread, will try to be brief)
My sister gets married in May and the guest list includes our father who I haven't spoken to for 20+years, and don't intend to see ever again, particularly not in public at an important event.
So I intend to tell her I won't go if he does. I'm not going to ask that he is not invited, who she has there is her choice, but I do expect her to tell me whether or not he is attending so I can base mine and my family's (partner & kids) attendance on that.
He's not a monster, he just pushed us out of his life many years ago so I made a conscious decision to live mine without him in it as the less painful option, rather than waiting for him to get in touch (he didn't), and my sister is fully aware of this. It's been a successful decision and has allowed me to move on from an unhappy childhood. Naturally my sister isn't estranged from him, although they had a few years of not speaking. I think it will also be pretty awkward for our mother (who has never remarried, to his 2 subsequent wives, one of whom he left her for) who doesn't really have anything to do with him either.
Sis hasn't mentioned to me that he's invited, which I'm a bit annoyed about, it's come back to me via another relative. I will say something to her about it when we next talk and I expect her to tell me I'm being selfish, I think she's a bit naive to expect us both to go, or for our mother to fully enjoy the day. I would be sad to miss her wedding but I'm not prepared to spend the whole event feeling awkward and uncomfortable, avoiding his gaze and that of all the other family members who are aware of the situation, or a possible confrontation. And I couldn't possibly imagine the photographer trying to gather 'all the bride's family' for a cosy photo. so AIBU to not go?