My 24f ex 28m harassed my best friend 23f

Ex sexually harassed (assaulted?) my best friend, his cousin I 24f was with my ex 28m for 2.5 years. We have a young child together. We recently broke up for unrelated reasons. My ex happens to be cousins with my best friend 23f. They didn’t grow up together and never really knew each other much until him and I started dating. Last night she told me on multiple occasions that he would touch her inappropriately, grabbing her ass etc. She never told me til now because she was scared, embarrassed, etc. I’m not mad at her for waiting to tell me. I can’t imagine how uncomfortable that was for her. But my world just fell apart the second she told me. Cheating, sexual harassment, and incest all in one. I don’t know what to do. I don’t know how I can ever look at him again. We have a child together, we have to talk and coparent and spend the next 17+ years doing so. So much betrayal and heart break and disgust and I just have no idea what to do. I dont think my best friend will want to press charges of any sort and I dont blame her. I just have no idea where to go from here. I feel like im losing my mind and dont know anything right now. I don’t know what’s best for my child. Any advice is appreciated I just have no idea what to do.