Do I tell my SO who sexually assaulted me as a child?

I was sexually assaulted by a close family member as a child. It's getting serious with my SO and he is close with my family and even the one who assaulted me. He knows that I was assaulted but not who did it. I've told 2 boyfriends and have been terrified that they would tell others now that we're not together. Do I tell him and upset the bond he has with my family or leave it in the past?