My grand mother name includes in legal heir certificate

Sir, both my father n mother was Govt employees, they bought some houses n lands,suddenly my father died in 2002,we are two daughters, my grand mother suddenly included her name in my fathers legal heir certificate though she was retired head mistress n getting pension n owned some houses. When we sold some houses in 2003 also, she taken 30% of amount. Now grand mother is 85 years old. How can we change our fathers land into our name ? My grand mother dies what will happen will it go to her legal heirs again? Is it correct in including my grandma name in my fathers legal heir pls explain? We are waiting for this question for past 20 years?