Family issues

So I do not get along with my boyfriend's mom and sister. we've been together almost 3 years, and they hate me and I hate them. they talked mad shit on me to my bf and said I was selfish and a bitch and to leave me. he wouldn't leave me, and they got mad again. I don't want him to feel as though he needs to choose me or them. but he's acting like he's choosing me which could end badly if he chooses sides. Lol so any tips on how to keep a relationship good with this conflict?