My Friend has an abusive father, what should I do?

My friend Emanuel has been a jerk to me recently. I asked my mom what was up and she went and asked his mom, we both were shocked to know that he and his poor older sister have a father, currently divorced from the family, who is physically and mentally abusing to the two children. The man is very wealthy, and every restraining order against him has been taken away because of how much money he has. The only way for him to get what he deserves is if the kids testify against him, which won't happen because they're scared to death by their abusive father. I really want to help these kids, my mom said it was private and to stay out of it, but I can't sit here and do nothing. I need options, I need advice.