Short version, DH and I are fine with his parents. We are NC with his sibling and SIL as they put us in a very difficult position (it's a petty reason initially but I've taken all the blame and even PIL still say they have no idea why because I was nothing to do with the situation and it's the BiL/SIL jealousy). Sorry I know that's vague!
Haven't seen BIL/SIL for over 8 years, they've never met our children, despite living in the same town.
BIL and SIL live and work with PiL (hotel business) and they're throwing a big wedding anniversary party for PIL next month.
PIL will be furious if I don't go but im just not comfortable going knowing that I've been made the scape goat for the BIL/SIL transversions. The last time DH tried to smooth things over with his brother he out right asked him what their problem with us was and BIL said 'her!' (me) but yet still couldn't tell us what I had ever done. Literally no one, myself included knows what we've done apart from one situation (had a baby together before they did and BIL at the time said to DH that SIL wanted a baby but he didn't as he knew she was cheating on him).
Anyway, DH thinks we should just go for his parents sakes but I know it's going to be all the people BIL and SIL socialise with as they all work at the hotel.
I've considered being ill that day but DH isn't keen!