How to proceed with this situation.
We are family of 5, father 58yrs Professor, mother 55 yrs home maker, we children unmarried, sister 32 yrs, sister 28yrs , me 26yrs. Now my father has sexual relationship with an SC/ST PhD scholar, for last 4 years. When my mother got to know about this affair, he used to say you doubt on me trust me, when the girl started calling more often and it was clear, people have seen my father and girl kissing on streets. he started saying it was once off, now the girl is troubling me, and she can get me too jail. so mother tells him to just get done with the PhD and have minimum contact. But seems he doesnt really care now, and goes at the girls place all the time. He will say he is going to office but would go and fix this girls curtains, have alcohol and sex with her, buy her gifts and take her to restaurants. So he is clearly into her, and does drama in front of us (children) that he is being troubled and he is trying to finish her PhD. Now I dont trust my father at all. And he mentally harasses my mother by saying youre stupid, you are illiterate you cant do anything. Inducing fear by saying the girl threatens to kill you. I want my mom to stay at current household and dad to stop mental harassment, or leave the house.