My boyfriend’s family doesn’t like me

We’ve been dating for a few months now and I know that his grandmother does like me. She’s the only one of his family I’ve met, and I go to her house a lot. I think his mom and dad are okay with me or don’t have an opinion either way since we haven’t met?

But his cousins.

I knew two of his cousins and actually had one of those elementary and middle school rivalry type situations with one of them before she moved away. I haven’t spoken to her since and she’s still friends with my best friend, and I’ve reached out to her since I started dating my boyfriend but she won’t have anything to do with me.

His other cousin that I know is a bit older so we never really hung out or anything. I thought she was at least okay with me because she would like my instagram posts and all that, but I posted pictures with my boyfriend for the first time on my birthday a few days ago. She immediately unfollowed me.

I don’t want to bring it up w my boyfriend because they’re his family and I know this is kinda childish. But it really is hurting my feelings that I’m not accepted by them. My only guess is that they think I’m not good enough for him.