Step mom selling late father's land w/o giving us share. What to do?

My mom expired when I was 3 years old and my sister 1year. After that my dad remarried and my next mom has 1 daughter. 2 years ago my father expired and after that now mom avoids relation with me and my sister. She also says false things about us. Now, it is all over & I don't need those inhumans, but there is a land property which was in the name of my father.

As earlier decided it would be divided among four. But lately I heard from few that the property is either sold or to be. What to do?