Boyfriends stepbrother

So Im 15 and I’ve been dating this boy for 6 months (were long distance but we have met irl) his step brother has been mean to me since the day me and my boyfriend started dating and I’ve always been really nice to him but .. he would call me a Wh@re everyday for 4 months straight. He’s always saying extremely mean things to me and making me feel bad about myself he’s always telling me to Ki// myself (knowing I’ve struggled with depression and past self harm) and all of that. But my boyfriend never tells him to stop or defends me.. He claims that he has but he never stops I’m getting really sick of it because I can’t be nice to this kid forever. And I really love this boy a lot but he won’t even defend me.. and sometimes he takes his stepbrothers side or let’s him talk stuff about me. I’m done with it fr but I need help!