Never mind NYD I would not be going at all.
I doubt the reason you have not been invited is down to you. Even if it was, no excuse for this underhanded behaviour. It must have been so hurtful. Especially how you found out. I sorry but I don’t think your sisters are innocent in this. If my parent(s) were treating my sibling like this I would be calling them out. If there was a reason why not invited I would be saying why.
You have not mentioned other relationships such as in laws or father. Understandable to only share what you feel conformable. The only reason I mention is can you think of people that do treat you right and focus on them?
Do you think being treated as second class comes from mother or stepdad. Could stepdad be driving it? Even if he was I would like to think mother would put child first or at least be honest.
I get you don’t want to rock the boat and be one to end things by going NC. However, you and your children are worth more than this. Please ask yourself what message may being sent to your children. Could it be sending the message that ok to treat them as second class?
It is hard when you do all the running. I speak from experience. I was the one that arranged things with my parent. I was often turned down. It was often that new partner would not like rather than them not wanting. I tried to have conversations how I felt. It was brushed over and told that is just how it is. I was never invited over at Christmas. I got a half hearted invite near NY. I was often hurt how I was treated. My other parent saw this and was upset for me. They were also angry. Why did I put up with it. They hated seeing me hurt by the latest thing. In the end i stopped asking if wanted to go somewhere as only hurt when answer was no.
I put up with sloppy seconds. I knew if I didn’t that would be it. I knew if I push the issue we could end up NC if I didn’t put the effort in. I felt guilty about being the one that would potentially end it. I keep thinking at least my parent is alive. That some not so lucky. In the end however, that wasn’t enough. I owed myself more. Too much negative headspace given to it.
Earlier this year I had things going on. Things dragging me down. I had an argument with my parent that would get the stars out of the sky for me. In this argument it came up how other parent had treated me yet again. I realised they were right. Over the years I stuck up for them. I couldn’t this time. I spoke to parent that I am NC now how I felt. That I was not happy how things are, Again I got that is how it is. We used to meet every week but I got to feeling that was more habit that wanting to have a relationship with me. I suggested not doing this but could still meet up. During this conversation it came up that their partner had an issued with our one evening as that was one less for them. This was despite spending all week with them as both retired. I think it was point I realised nothing was going to change. I suspected my relationship or lack of was heavy due to their partner. I get when you have a partner you need to think of them but not at the virtual exclusion of child.
I left the meeting up to them. Even if it was just a simple suggestion such as a coffee that would have been fine. I knew this would probably mean the end and it was. I would be lying if I said it didn’t make me sad. However, I felt better as headspace not being taken up. I have relationships that are two way. While they drive me crazy sometimes and I am sure other way too I know we have each others backs and they truly there. I cherish these. Even more so since going NC with parent.
I know is difficult but do you really want a relationship with someone who makes excuses not to see you. You have only seen them twice this year. It is either a one way relationship or you/husband/children have issues so they want to want to avoid (personally I think that unlikely). However if you can reflect on your/their behaviour and see why it may cause issues I think would work better with LC/NC.