My sister is pregnant by an abuser

Ash • Married 8.2.2014. 1st Boy 11.24.16. 2nd Boy 8.27.18
I posted about this before but in a different context. My 19yo sister is pregnant and has decided to keep the baby. That's great news. Problem is, she wants the father involved. He had beat her multiple times, destroyed over a thousand dollars in her property, got into a physical fight with my uncle because my uncle caught him hitting my sister, he has severely disrespected me, my mom, and my youngest sister countless times. My sister had a restraining order against him but was obviously still seeing him because she's pregnant. I have offered for her to live with me to get away from him. She won't. Now she's having a baby and he apparently wants to talk to our family to apologize. She wants him involved. Am I wrong to step away because I can't sit and watch the poor innocent child be brought up in that? I originally was going to do all I could, offered her again to live with me so she could use her money for the baby and she wouldn't have to worry about money while not working (her job doesn't offer paid leave). But after her saying he will be living with her and the baby, I can't handle watching and worrying if that psycho is beating my sister in front of the baby or worse, hurting the baby. He has no job, is in drugs, he's been leeching off my sister for 2 years. I'm just so heartbroken. This is especially hard because I just delivered my son 3 weeks ago and a sweet baby should never be subject to that.