Late father house illegally sale by the money lender what to do

There is one house of my late father in District: Muzaffarpur, Bihar. My elder brother had mortgaged my father's house in need to cover my sister's marriage expenses with a money lender in the year 2004. In the year 2005 my elder brother was arrested in a criminal case and still he is lodged in jail. Taking the advantage of this fake sale deed papers was prepared & money lender is shamelessly transferred and registered the my father house to third party in the year 2012 & now third party living in my father's house as an owner for since year 2012. When I opposed and objected the money lender for this act in return he threatened and told me that I can't do nothing whatever legal course I take in the future. I was not aware that my father property was illegally transferred to third party by the money lender because since my elder brother arrest I was working in Wardha, Maharashtra to earn my living when I visited my native place Muzaffarpur, Bihar in 2015 I came to know that my father.