I think you've had a pretty terrible childhood and it left you scared and confused. I think you never acted with deliberate cruelty. I think you were a child (with a child's brain and understanding) and while you are still a child you are now on the cusp of adulthood.
So let yourself draw a line in the sand. You can't magic your relationship better with your brother and sister. All you can do is continue to be the best brother you can be. I believe they will slowly learn to trust you again.
At the end of the day, there is a good reason why internal law says it is absolutely wrong to imprison children forever or execute them. Children are still growing and maturing. You can leave this behind you. You just need to have faith in that and stay strong. I think the very fact that you have become a good, self-reflective person out of such bad circumstances says a lot about your character, honestly