How lovely. Your brother is the Golden Child, you're the Scapegoat, and your mother is the Narcissist who must have her own way all the time no matter how it hurts or inconveniences anyone else. Because she is the ultimate centre of the universe, don't you know. And heaven help anyone who dares to say 'No' to her royal majesty. I can only imagine just how ugly she can get when you refuse to bow and bend to her every whim. She probably gets a special thrill whenever what she wants causes YOU the most stress and upheaval.
I don't think she even wants your son there so much as she wants to stick it to you as painfully as she possibly can. Your current DH is a saint for having put up with this. OP, it's time to realize that your mother isn't going to change, she's always going to put your brother first and stomp all over you, so, like everyone above has said, cut the cord. She doesn't love you, she doesn't give a flying monkey crap about anything to do with you unless she can use it to hurt you. Stop putting yourself out there to be hurt and inconvenienced. You're not the only one affected by this, you said it yourself: your current DH, your son, your Ex are all being dragged along for the ride. Time to get off the train and start doing what YOU want no matter how she whines and guilts and tantrums. She's a toddler, and you don't tolerate tantrums and guilt trips from toddlers, do you?
Well, you've certainly nailed it, that's for sure! You know, it's funny that you compare her to a toddler. At Thanksgiving, she threw an ugly tantrum because things weren't going her way. We had only been there for half an hour. I'd had enough of it, so I went into the kitchen where she was tantruming, looked her straight in the face, and told her that if she didn't get herself under control, DH, DS, and I were leaving. She argued and fought it for a few minutes, but when I didn't back down she dissolved into tears. The tears were, "I don't want the holiday to be like this," rather than genuine remorse for her behavior. She didn't feel bad about what she did. She felt embarrassed about getting caught.
She's a narcissist through and through. And yes, my brother is the Golden Child, and I'm the Scapegoat. It has been that way as long as I can remember. She does in fact create situations that are difficult for me to manage in an attempt to teach me some sort of lesson. I struggled for a long time with trying to understand why nothing I do is good enough. The truth is that it's her problem, and I don't have to take it on myself. Being an adult has its privileges, and I can choose differently when she tries to set me up.
I do pretty well for the most part in staying off the narcissist train. Where I continue to struggle is in situations that involve DS. I think he should have some semblance of a relationship
with his grandmother, but under controlled circumstances. It might sound odd that I haven't given her the cut direct. I came pretty close about 5 years ago. I'm willing to do holidays and birthdays, but beyond that we don't see my mother much.
DH has been incredibly supportive, and I don't take that for granted.
He was there for the Thanksgiving blow-up (there are many more details involved that I haven't explained here), and he saw her narcissism in action for the first time. He couldn't believe what he was seeing.