Sorry this is long - need to give a bit of background. It's been going on for weeks and I really need some help.
DS moved to a distant foreign city (other side of the world) in January to start a postgrad degree. The only person he knew in that city (where he'd never been before) was my DSis, who lives there and who has been a wonderful aunt to him and like a second mother all his life. I think, fairly naturally, he and I both hoped that she would be able to give him a bit of help settling in in this new city, e.g. give him somewhere to stay while he found uni accommodation. Well, that didn't happen as she and her new partner decided they had to go on holiday at that time. Was a bit disappointed, but anyway he got on with it, found a friend of a friend who let him stay while he found a flat.
Move forward a couple of weeks, and DSis comes back from holiday. DS asks if he can visit and stay for a few days as he would like to spend family time with DSis and also felt he had stayed long enough at friend-of-friend's house (he was moving into his new flat in five days). She says yes, so he goes to her house.
By day 2 the atmosphere is unbearable. Partner of DSis does not like having him in the house and puts a him-or-me ultimatum on DSis. DSis crumbles and kicks DS out, literally onto the street, giving him an inflatable mattress and a few pans and towels. He manages to get into the flat a couple of days early and camps out until his furniture arrives. In the meantime DSis sends hysterical emails left, right and centre telling everyone how appalling DS is (not true). Her DP sends me an incredible email telling me he's lucky he wasn't chucked out with a black eye and I should take off my rose tinted glasses about him. Apparently amongst his sins were "expecting to be fed". Please take this in the context of 1. my family is always warm and hospitable to each other, 2. they are not short of money so could certainly afford an extra place at the table, 3. DS is basically a broke student, 4. he brought the usual kind of contributions and helped out around the house like any well-mannered guest.
All very upsetting and I cannot believe that my much loved sister has behaved like this towards her nephew who she has always cherished. Literally cannot believe it. Still I am trying to make a reconciliation and just ask her to apologise to DS. No apology is forthcoming, well a little bit to me but not to him.
Now for the wedding related bit. I am going to visit DS at Easter. This has been planned for many months. With this date in mind DSis organised her wedding to the above mentioned partner for when I was there. I love my sister and want to support her and celebrate her wedding. But I feel she has basically sacrificed my son to her partner's whims. Her DP has also grossly insulted me and DS (sent DS an email saying he was never welcome again). She has also rescinded the wedding invite to DS. I just need to say again, what a long and loving relationship she has had with DS all his life, so this is just an unbelievable turn of events.
DS says he will feel betrayed and unsupported if I go to the wedding. Elderly DM is having a hysterical breakdown at the family fall-out. DSis says I should support her, even if she acknowledges she did the wrong thing (which she kind of does), as she has supported me in past difficult times (true). I've heard nothing from DSis partner who is at the bottom of all this and who sent me the horrible email. I don't particularly want to ever see him, but I don't want to destroy my relationship with my sister. I also don't want to betray my son's trust.
What do I do? Son or Sister? Wedding - yes or no?