I am writing this for DP.
DP fell out with his family 5 months ago after they continuously left him out of family celebrations for big events and would post pictures with captions like 'The Smith Family', with DP (and me) being the only one missing. They also lied about how this occurred, saying it was spontaneous etc, even though his brother literally lives in a different country and only ever comes to England to stay with and see his parents. One of the main areas of dispute is that his Mum (a narc through and through) acts preferably towards his sister in every way - it is glaringly obvious.
DP went low contact. However, we are getting married in a few months and his parents hadn't RSVP'd. DP text his parents and confronted them, wondering why they hadn't even tried to see how he is (for example he was in a major car accident and they knew about it but ignored it). The main point was regarding the RSVP but I think DP also used it as an excuse to speak to them. Whilst DP has gone low contact, he didn't tell them this, they had an argument involving his sister 5 months ago and no one has spoken since.
All wedding invites and messages sent have been read and ignored.
Anyway, the big argument that was the catalyst to the fall out involved his sister and she was just as complicit (she organised a family event and didn't invite DP). However, I do think his mum is still the grand orchestrator of problems.
At the weekend, we were going to a NT site near SIL (we live 2h from them, the park was 20 mins from theirs) and I agreed with DP to message her, asking if she wanted to talk and get a coffee. She agreed and brought her husband and daughter (DN) along. It was the most incredibly uncomfortable small talk conversation, and eventually DP got the nerve to say something. When he brought up The Event she said she didn't come to talk about it and walked off.
DP is now unsure what to do.
Following his texts to his mum around the wedding, his dad asked if they could meet and hug it out. DP responded saying 'if they want to discuss what happened, arrange a place/time and let him know'. They read the message and never responded, this is over a week ago now.
What next? I feel like SIL's reaction was so shocking even to me, that I felt so uncomfortable. I feel like it's a nail in the coffin to the relationship.
So DP has asked what to do now as he trusts the MN people. Including your opinion regarding our wedding.