Partation

My grand father (mother’s papa) has property in pune but in the year of 1988 my uncle (mom’s brother) has transferred all property in his brother in law by sale deed. Actually not sold he transferred property in his brother in law. My grand father died in the year of 1995, and then my uncle transferred all property in his wife (my aunty) by power of attorney on his brother.

 now he is has sold all property to builder  to 151,0000.00/-  (one caore fifty one lacks) to builder , he had made power of attorney from my mom in the last year without giving a single coin , when my was ill and suffering from Brain cancer, she is no more now , she have 1/7 share in the property, so what to do now , what will be stamp duty for civil suit, and will the sell deed can be cancelled. builder have made 7x12 sheet of revenue dept on his name what is procedure to cancellation the 7x12 sheet of revenue dept.or any other any producer without going in civil court action due to financial problem . What should i do please help me and advice me.

Thanks & regards