Re the Sis - I don't think she's embarrassed. I think she's blaming you for not taking him back. Even if blood IS thicker than water, what reason could there be for not even asking how you are???
She thinks you're over reacting. They probably discuss it and it reinforces the same thought with your ex. If he had other folk in his life telling him to accept that he'd ruined his marriage etc then he may actually sit down and think hard about your current situation.
Instead, he's still outraged that your being 'unreasonable' and over-reactive, probably because his family think it too.
I'm sorry to even type this out LNM because it's a disgusting, disappointing and treacherous to realise that his family can't even support you. Should you be MY Sis in law, I would. As much as I would love me DBro, I would understand and see your hurt.
I'm so
on your behalf. This is wrong wrong wrong on all levels. I Agree with the others. Formal letter, possibly through Solicitor about boundaries and issue with your Dd's. I'm wondering whether the mediation someone mentioned upthread ages ago will help him 'hear' and accept what you've been saying? That's your call of course and it will be draining, but it may hammer the message home that things are over.
The solicitors letter may do that as well.
Just a few more things to consider LNM. Wish I was closer - I'd come over and help you fix that chain and drink your wine