Non caring of father after remarriage

My wife are two sisters.after the death of my mother in law in 2010.At the age of 52 my fathetinlaw remarried a 28 yrs old divorcee who has one girl from her first marriage After remarriage my father in law's whole attention got diverted towards her.He stopped paying attention to his daughters' needs.And it's worth mentioning he is a severe alcoholic.He started beating and abusing both his daughters.This continued for 1.5 years and in between my marriage took place and my wife came to my house , leaving thher younger sister at home alone to face the torture and humiliation at the hands of drunk father and step mother. She performed very badly in her 10+2 exams.Seeing her future in danger she was taken by her maternal uncle to his house.She is doing BA+LLB 5 Years course at jaipur for which fees is 1.5 lakhs per year.Her mama ji being a farmer can't afford this much of financial burden.Hence we went to her father to pay fees as he is an ex merchant navy.He plainly said I don't have any relationship with her and no question of paying fees arises. House in which my father in law resides was on the name of my deceased mother in law.My idea is to take legallpossesion of the house.and rent it out.The same amount will be utilised for study of my sister in law.My father has a plot of 300 square yards on his name whose market value is 40 lakhs.He is a pensioner also. Plz guide the way out I am very serious of the matter