Cancellation of sale deed of self aquired property

Dear Sir, Now i am the owner of the land. I have purchased the land from my grand mother in may 2012 in the form of sale DD. The land was actually aquired by my grand father few years back from other caste person in the form of sale DD which is for reasonable price 10000/- around. He died on 29 th march,2012. After two months My grand mother wanted sell the land for her livelyhood because her son not taken care of her. So I purchased the land in may 2012. My grand mother has two daughters and one son. Age wise names Laxmi,Lalitha and Narender(son). I am the son of second daughter Lalitha. All are married and separated families. Now, my uncle filed a petetion that it is a joint family property, share the portions and cancellation of sale deed. And forcing his mother to file a complaint to cancel the sale deed willfully, they are demanding money from us. He sent a notice to me that " claim: suit for partition and seperate possession and cancellation of registered sale deed" According to tahasildar or MRO records the land is on my name from may 2012 and i am cultivating the land. can it be cancelled? Please give your valuable suggestions. urgent. I am in dilemma. what to do and how to approach Regards