inheritance property of my father

I am a 15 year sole son of my father , there is about 2 hector ancestoral land in the name of my father through my grandfather and grand mother .my father is involved in extra martial affairs with an muslim girl .he is going through bi polar disorder ans few other psychiatric problem . He behave rudely with us and my mother and be busy on phone with that muslim girl . We are doubting that he may sell or transfer land property to her .kindly tell us what is the legal way to stay out the land