I am a biracial 22 yo female. My bf is white. His parents fully accept me but he’s got an uncle who has made unbelievably racist comments like “she’s a half breed.” He didn’t say it to my face or my bf’s but it got back to us. He’s my bf’s father’s brother.
Your bf's parents are the ones that should have a talk with him first, and that should be followed up with the four of you telling him that he is welcome as long as he does not say such disrespectful things.