My uncle selling ancestral property without consent

We have ancestral property in Solapur. My Uncle took power of attorney from my Father in 1972 and built the three storied building on it and rented some part of it. After death of my father in 1988 , my uncle took general power of attorney from us (me and my mother) to handle all transactions related to that property. Now he wants to sell off that property without my consent. How to stop him doing that ? The 7/12 on the land has three names My Uncle, My mother and me. But the construction on the land has power POA from my father first and then now General POA from me and my mother.