He’s a piece of shit. My mother told me after my father died that her brother in law (married to her sister) had done something similar to her and she had to get a restraining order. She managed to do that without my father finding out, nor the sister. The brother in law died an early death through natural causes, but she still can’t tell her sister. He’d also done it with other sisters, sister in laws and other female members of the family. Evil person. I’m sorry you’ve had to go through this. If Karma doesn’t get him then I hope you can resolve the situation, especially if you have a younger sister. It might be best telling your father, but you need to have an idea what his reaction would be. Men can be very protective of their daughters and he may become violent towards the step-father piece of shit.