AIBU to not look forward to DB's wedding and even consider not going?
Background:
My DB's wife died after a brave fight against an illlness 3 years ago. She was a wonderful person who i loved and they had 2 young children. Shortly afterwards, DB met someone else. They became serious very quickly, she moved into his house with her children 18 months ago. I don't know her very well as initially i was upset that DB had moved on so quickly and publicly and not considered the feelings of his late DW's family. Over the last year, despite mixed feelings about DB's new partner and their relationship i have made an effort to become friends and spend time with her as it was obvious that my DB was serious about their future together.
My parents split up 8 years ago after my F had an affair with a 'friend' of my parents "OW" who he lives with now. He treated my DM very badly over several years , it came out that he had several affairs and done other horrible things during their marriage. There was an acrimonious divorce and he behaved very badly towards me too. I decided not to have a relationship with him. He was not invited to our wedding and has not met DS 1year. My DB and DS still have a relationship with our F which is their choice. In the last 6 years i have seen F twice, at DSis wedding and at late SIL's funeral. I have always said i will not go to any event e.g. christenings where F will be. These 2 events were very stressful for me as F who is very thick skinned kept trying to talk to me despite me keeping my distance.
Now DB and his DP have got engaged. DB suggested a small wedding abroad but his DP wants a big wedding with all their family around them. DB and his DP have stayed with F and OW. DP (bride) thinks that my DM should be able to move on and spend time with F and OW, she does not 'get' our family. DM has done masses of childcare for them and been kind / generous to DP.
The problem: this wedding is going to be a complete minefield. Despite my slightly mixed feelings, i do want to support DB at his wedding and welcome his DP into the family - he deserves to be happy. But DB has form for being really tactless - i'm sure he will invite both DM and F and probably OW too. In the past F has refused to attend events if OW is not invited . DM will attend if F is invited but will be very upset all day. DM would not attend if OW was there. I'm dreading the whole thing, considering a boycott if OW is invited and only attending for a short time without dS if F is going.