Senior Citizen parents harassment & their welfare rights

Hi, i am here to seek help for my old parents who are being bullied & tortured by my brother & sis-in-law. We are 4 siblings, My elder sister married & settled, my younger one studying nursing outside, I am still a bachelor man looking to settle down in near future & my brother who had a love marriage against my parents will. right now i we all stay in the same house as in myself my parents & my brother & his wife & their 8 month old son. my sis-in law called the police the other day threatening my parents & me even though my mom takes care of the baby as she just leaves him & goes for work. the house is owned by my father who is a senior citizen. She abuses my parents & my brother doesn't say a word. I feel helpless as I am not married yet & she threaten to sue my in case of sexual harassment. if this happens , no girl will ever trust me for marriage & also my reputation is at stake. when my parents told my brother to leave the house & take her away, he refused to go & said they will stay here only. My dad was a simple driver all his life in Delhi , who out of his hard earnings , raised all of us. please advice.