Posted 05 June 2015 - 01:37 PM
That's a tricky and not fun situation. Your parents don't really deserve the time of day from you at this point after having behaved as they have for so long. Being mad at them is perfectly normal. And perhaps your son is better off not knowing them.
As to your in-laws that's where it gets sticky. Having had a relationship with you and your mum makes it less of a cut and dried situation. Should they still be going to this party even though this is all going down? Probably not if they want to hold on to relationships on both sides. There are diplomatic ways they could go about it without offending either side (much)...like they could send a gift and card, but not attend. They can protest the treatment of you and yours without offending your parents too much by doing so.
That said, I will mention that you should under no circumstances make your in-laws "choose" between you all with any kind of ultimatum. That would not be fair to them since they have relations on both sides. I know that sucks because it definitely feels like a betrayal. I'll use a personal anecdote to give me reasons for why I feel this way. When I met my best friend, whom I've known for upwards of 16ish years now (he was the Best Man at my wedding, and I'm his daughters godfather) he was still in University, and had a small group of friends. Amongst those friends was one girl who I ended up dating. I dated her twice. the second time I dated her was the longer of the two dating periods (2 years). I lived with my best friend at that point (a few years after Uni ended) and the girl was living with another of the Uni friends, and we used to all hang out together. Then shit went south. The girl and I broke up, and I was pretty sure she'd either cheated on me, or lined up the next guy while we were still dating. I was broken and upset. Throughout this all I never once said anything to my friend about his friendship with the girl. She, on the other hand, walked up to him one day a few weeks after the breakup and told him he should "choose to stay friends with only her because she was friends with him longer. He told me later, after he'd cut ties with her completely, that he stayed friends with me because I never, ever asked him to choose. To this day I hold that up as my yardstick in such situations. You should feel upset about he whole thing, and you will feel slighted and betrayed by your in-laws. But in the long run you just need to let them live their lives how they wish and interact with who they choose to. It's a shitty situation, but it could be much worse if you bring it up as a choice they should be making. One over the other.
TL;DR I get your upset and sympathize.
"When the last tree has fallen, and the rivers are poisoned, you cannot eat money, oh no." ~Aurora
"Someone will always try to sell you despair, just so they don't feel alone." ~Ursula Vernon