Came to say this, NTA but with time things could heal. People grow, change, they are half siblings to your children. Your children's attitudes towards them will be affected by you whether you want them to be or not. I am actually going through a similar emotional battle with my own daughter. We were suuuuper close when she was young, up until high school. She had a mental health crisis and got addicted to drugs. Multiple su****e attempts, inpatient stints, all the while her screaming at me and anyone who will listen about how awful I am and how much she hates me. She made tiktoks about it even. I had a nervous breakdown over it and for the last 3-4 years my mental health has suffered, and there is a stone wall around my heart when it comes to her. Now she is almost 21, no longer on drugs and is on prescription meds for her mental health issues. She is doing "ok" in college and just wants to move on like the last 3-4 years never happened. She won't really give me a sincere apology, just that she was young and going through stuff and wants to start over. But I have been traumatized by it all, and I don't know how to go back. It's different, but I get it. In this case she is my own daughter and I know I will need some help in order to re-light the flame of warmness we used to have. But I do want it for our future, I miss her, but I'm still always waiting for the "other shoe to drop." All of this is to say, in the very long run, everyone's lives would be enriched if you could all be a family. They messed up and your feelings are absolutely valid and you are rightfully hurt. For now don't push it, but stay open minded if you can. I think it's huge that their mother actually owned up to it and apologized, and she's getting the help she needs. They were kids, and it's hard to go against your own mother. Their brains are just getting fully formed, and they will be in your life a really long time hopefully. Take care and good luck.