Why do they do that

My biological dad abused my mom physically and emotionally when they were together. I was too young to remember it vividly but I have slight memories of my parents fight and hearing bangs against the wall and screaming but it’s not very clear. None of us have anything to do with my biological dad he was tried contacting me but I don’t want to hear from him. He was an alcoholic and probably still is I was under the age of 10 last time I saw him and never have to see him again. My mom has told me gruesome stories about what he has done to her in the past. She eventually had him arrested and that started a revolving door of him being in and out of jail. He deserves it though he’ll die alone with no one that cares about his abusive ass