My father is so cruel with my mom after his mother expired,and everyday he find ways to quarrel with

My father is so cruel with my mom after his mother expired,and everyday he find ways to quarrel with her and other family members, as i live away from my home ,he tries to shows me that he never had hurt my mom, but I know my father very well, even I know his behaviour since my childhood, my mom cannot handle him anymore, she is now in depression and mentally disturbed, also even after 20 yrs my father didn't accepted my brother as his own child and also he was careless and cruel about my brother,my mom never shared this things with others just because what people will about them so she is always afraid of it. We live ina joint family and my father don't talk to anybody and purposely finds ways to disturb everyone's mind peace and he throws anything here and there, speaks bad words for uncle and aunt and everyone ,but when we ask him to leave this home and live anywhere you want if you don't like this family,he says why should I go somewhere else , we all are fade up of this everyday t