Multiple ownership claims to same agricultural land

My aunt (sister of my father) doesn't had children and during her old age I had taken care of her. As I was taking care of her severe illness (cancer) she promised to register her agricultural land which was in her name. Meanwhile my younger brother fooled my aunt by making her to give Power of Attorney to Person X. And the Person X sold the agricultural land to my brother through sale deed. I and my aunt was not aware of that. As soon as we got to know about this my aunt registered the same land immediately to me within 15 days though gift deed. She was expired within 3-4 months after registering the property to me. And all the documents( chitta, patta, EC, Loan) are all in my name now. I have been growing crops and occupancy of the property for the last 30 years is me. Now, my brother is coming to claim the ownership of the property as he bought the property from Person X who was given power of attorney from my aunt. Whose documents is the legal one and who can claim the ownership of the agricultural property?