Joint name property

I have a property purchased in 2002 (Mumbai) in the name of My sister as 1st owner, me as a second owner and my father as the third owner. The investment in this property at the time of purchase was 12,25000. My father gave cash of 158,000 and the rest was a home loan of 10,42000 balance money 25000 was paid in cash by me. The home loan was also in joint name of all 3 of us however the entire loan was paid from my bank account with my salary. My sister understands that she did not pay anything in this house and hence is willing to give me the rights as a gift. My father claims that he has paid and wants his share. My father left the family and stepped out of this house breaking all relations with my mother and us his 3 children in 2005. Its been 12 years that he did not give any money to my mother who has been a housewife all her life. I have been the sole individual to take care of all family responsibilities financially. He comes back now asking for money from this property which I have paid nearly 85% of the total value. Without any consideration of share for my mother or any compensation for our emotional trauma that we as a family had to go through for the past 12 years. My mother and him have not divorced yet they have been living as separated without any communication for 12 years and she has yet to claim her alumni. We seek your professional advice as to how can we deal with this situation. Thank you.