My Uncle sold his share of property to us without consent of his children

We are part of a hindu family. The partition of our ancestral property took place between my father and his brothers in 1988, with the mutual understanding of the brothers via a registered partition deed when my grandfather was alive.  As part of this partition, my father and his brothers got 2.5 acres of agricultural land from my grandfather.. In 2006, my uncle (father's younger brother) sold his share of property (2.5 acres) to my father. My uncle has two daughters and one son. His two daughters were majors and his son a minor when my uncle sold the property to us.  Also, note that he sold another 0.5 acre to my other uncle (my father's other brother) in 2004. In the sale deed that my father has purchased from my uncle, the signatures of my uncle and my aunt's (the uncle's wife) are there. I'm 32 years old now, and my brother is 30 years old. Are the property sales made by my uncle to my father legal and valid?? Now, one of my uncle's daughters has gone to court to reclaim the properties sold by my uncle. What are the legal remedies available to us ? Is there any reason to be concerned about the properties purchased from my uncle without the consent of their children if we go to court to reclaim them? Do we have to pay them back the sale considerations from our pocket, or is our father liable to pay their children?  We wanted to know how we, the purchaser, are responsible for the sale made by my uncle. Please advice and guide me in detail. Even though the purchase had happened with my uncle & aunt intent but now after 16 years my uncle's children are coming back to reclaim the properties. My uncle and aunt are still there and indirectly supporting their daughters.