It’s tough to know what to do when family is estranged and 100x more when there was abuse. The only advice I can think of is you need to protect your heart. With their free will, people have the freedom to do good or harm. And those actions often have painful consequences. Since you see and are aware of the abuse, you want to keep yourself mentally, physically, emotionally and socially sound. By choosing not to follow in those footsteps you are doing good already. If you choose to Offer the olive branch of peace, just be aware they could accept it or reject it. You offering the peace is very very good, but if people use your kindness to hurt you, you need to distance yourself from that. No person should have to endure abuse and no one deserves it. Lastly time is a weird thing. Your sibling may come around and reconcile when they are older. But whether they are distant, mean, odd or whatever keep you own side of the court clean. That way they can not accuse you of anything.

I hope this helps.

Stay strong love, I know what this feels like