I hope you will see a counselor/therapist; you have no way of knowing if your dad has molested your siblings....strength has nothing to do with it...it is a psychological thing...I doubt he would have stopped if you had told him to. It wasn't your fault; you were a child......we trust our parents and that is why this is so manipulative; they count on your silence; this was a crime.....Yes, please talk to a counselor/therapist.....sadly, it is all too common. At some point, you may want to consider talking to your siblings.....it is the secrecy and silence that is so damaging in families.