Have you ever ended a relationship with someone because of their kids?

I feel like a terrible human being. I just don’t like one of his kids and it’s because of his parenting. He has two, a 13 year old girl and a 15 year old boy. The boy is so selfish, I try to remind myself he’s a child, but it’s too much. Dad has full custody because the mom has severe schizophrenia and addiction issues. So I think part of his parenting is because he feels bad that their mom isn’t around. What really bothers me is that he treats his kids differently. He lets his son do whatever he wants (he has girlfriends, gets bad grades, goes anywhere anytime) and he doesn’t allow the same freedoms to his daughter. She has to have good grades, isn’t allowed to date, or go to sleepovers. He says it’s because she can get pregnant. But it takes two to tango and his son can just as easily get a girl pregnant. His daughter was recently sick and she was treated like nothing was wrong. But his son got a cold and he waited on him hand and foot. I’ve tried talking to him about it and pointing out that you’re treating the kids differently and the girl notices. He says his son needs extra attention and makes excuses that he’s airheaded, or his hormones fog his teenage brain, or he’s just a jock and doesn’t need good grades or to know how to do things. Neither kids are ever reprimanded and get every single thing they want.

We’ve been dating 2 1/2 years and recently moved into together. I’ve tried to step in when his son is being selfish and disrespectful towards me and saying hey this isn’t okay. Then dad steps in and says he doesn’t need to be in trouble and it’s emotional abuse to scold him. He told me I need to mother and coddle his son because he doesn’t have a mother but doesn’t ask me to do the same for his daughter.

I’m kind of sitting here like what the fuck? Who the hell is this person I’ve been with for almost three years? Am I in the wrong for feeling this way?