Sister wants an apology from my boyfriend for calling her a bitch 3 years ago

I started dating this guy recently and he's really sweet and really funny. Problem is when I showed my sister his picture she said he publicly called her a bitch on Tiktok 3 years ago. I don't have tiktok and I asked my boyfriend about it and he found the tiktok where he stitched her tiktok. Before I say what my sister said just know we come from a family that doesn't really prioritize mental health. She was saying how she believes we need to get rid of mental health hospitals because she doesn't want her tax dollars paying to try to keep crazy people alive and that years ago we used to euthanize schizophrenic people and bipolar people but we stopped because of snow flakes and now we have these crazies ruining the lives of people who are normal. My boyfriend has a brother who he cares for who struggles with depression and schizophrenia and he told my sister she's a horrid witch and told her first off fuck you bitch and that she thinks she deserves to be here more than mentally ill people and how he has worked in mental health hospitals and would rather be around them than spend one minute with in a room with her. Then starts educating people people on schizophrenia and how hard it is to live when you have splits in reality. He reacted to some more of my sisters "hot takes" and more or less called her a horrid person. He also had 2 mil followers at the time and my sister got hate and that's why she stopped posting on tiktok. So she wants an apology from him if he's gonna be part of the family. I feel this puts me in an awkward position because he does still take care of his brother and feels very strongly about people with mental health issues or special needs. So I don't think she's gonna get that apology.