From this very vague description.

A man meets a woman and dates her, they end up moving in together but the woman has an adult(?) son who is very protective and ends up being the major reason behind their break up. I think he actively tries to sabotage it.

I believe there is a significant scene with white sneakers. At the end they might get back together.

Well, if what i understand is right then...
Adults are a problem.
I am not really good, but something near that? where adult is a problem that makes the woman and the man's relationship breaks.

The woman's adult son who still lives at home is the problem. By adult I mean 18+

I know, then what is the problem of this son? doesn't he breaks their relationship?

You are miss understanding this thread completely please stop

step brothers?

Negative. I think it's a drama not a comedy. Probably should have said that. It was on Netflix if that helps. I also believe it wasn't a very popular/well known movie.