What can you do really? They're adults with their own lives.
I split up with ExH, my DDs dad, years ago when they were little. Now grown they're off here & there travelling, 1 is engaged, they're living their lives. Evrn I don't see them much these days.
DDs don't dislike their dad but they didn't grow with him so perhaps that's why they don't make a huge effort to see or be with him.
He's remarried, they're polite to his wife, theyre ok with their step-siblings when they meet, but it doesn't seem to be a priority in "we must actively make an effort to see/be with them' way.
So it's just one of those things really. No animosity but no huge interest. I'd think this situation is quite common, people tend to deal with immediate family in their world ie, who's around.
I've not seen my own step-sister for 3 years or so. Again - non-issue with her but I grew with my siblings so they're my 'go to' family that I'm close with. I don't visit my dad much although we do speak on the phone. He remarried and had more children so obviously he wasn't present in our family home. Dad's ok but I've no big urge to maintain strong ties.
It's a shame you're holding anger about this. You don't like their behaviour when they're around anyway. You have your partner and children, you could just let it go and accept you can't order people's lives. You just have to live yours.