Stupid is!!!

So my sister has this guy that she's been dating for six years. She has two children with him. He's a large bowel movement in my opinion. He doesn't have anything. No car, house, job,etc.. plus he has like three other children that he doesn't support. He talks to the children with no respect. Curses at them and she doesn't say anything! Stupid, right. Someone help me to understand what might be wrong with my sister. She'll be better of dating a god damn rock. Is she just a fool in love? I've told her that she deserves better but she doesn't seem to care. This chick has wasted a lot of her youth with him. I think that's a very sad thing. It seems like she's afraid of him. She still living in my mother's house so that's how I know how he treats her and the kids. I've prayed for and hopes that she will wake up. It seems to be getting worse. She's 28 years old with three children who my mother and I are supporting. I wish that she would eliminate his super sorry ass!! He even lives in my mother's house. By the way happy 😊 Valentine's Day!!!