AITA for not wanting to be the person responsible for breaking up a family

I teach 7th grade western hemisphere. One of my students is a very kind kid. Just has a lot going on at home. He has like one friend. Very bad hygiene which I'm sure is due to depression and has been in and out of mental health facilities for self harm. Mom updated me even though she doesn't seem to like me much because he's told her I'm his favorite teacher She acts so rude and hostile towards me. But she does tell me when he's changed medication. Etc. Etc. He also tells me he doesn't get much sleep because his parents are constantly fighting every single night.

I went out with my sister for her birthday to a club and she ended up dancing and making out with a guy there. I had a parent teacher conference with my students parents Wednesday. Both of them. I have never met his dad. I see his dad. Dad looks like a deer in head lights because I know he remembers me from the club because he was making out with my sister. Mom introduces me to her husband and we talk about this students grades.

I tell my sister and she's saying I should have exposed the husband. I think that's weird. In their kids teacher. He's got enough going on. If Dad gets caught he gets caught. I'm not gonna be the one to break up that family. She is telling me I'm obligated by girl code. She was the one making out with him. Why isn't she obligated by girl code? Anyway I don't want to get involved with that part of my students life. Does that make me an asshole?

Edit: I have made some CPS reports. They just haven't done anything