People do things not necessarily because of something you did or who you are, but it’s a reflection of themselves. Maybe their inlaws were hard on them and they do the same to you. Maybe they don’t like your boyfriend giving you more attention than to them. Who knows.

My siblings’ spouses don’t like my mom and it goes both ways. At some point you have to accept that you will not have a relationship with them and to just be cordial with them when you do have to be in the same room. You don’t have to get along with everyone but just be civil is enough when you have already tried.