Contact with abusive Biological Sibling

I'm an adult adoptee in my late twenties, adopted as a baby. About two years ago, I decided to get in contact with my biological parents, which has been slow but decent. My biological parents stayed together for several years after they put me up for adoption and had another child who is about six years younger than me. This person, my biological brother, comes across as an angry and abusive person. Our first point of contact was extremely aggressive, with him insulting me and my friends via Facebook and spouting racist and transphobic nonsense. Since then, we've had one phone call that was acceptable. Every other time he's contacted me has involved him insulting me and being very demanding with my time and energy. I've been in different relationships with abusive people before and I know that my biological mother had an abusive boyfriend who treated him poorly. I feel bad that he had that experience, but I also am not interested in starting a familial relationship with someone who shows signs of being abusive and emotionally manipulative. How do I set healthy boundaries with this person, especially as I would still like to have some relationship with my biological parents? Help please.