It is not clear if the GPA and will executed by your father and your uncle in favour of eachother, with respect to the respective shares in the properties, are registered or not.
All the four (2 GPA, 2 Will) documents were registered in 1994. My uncle sold the property he was living in using the power of GPA made in his favour by my father, but my father died in 2001 without doing anything. After my father's death G.P.A. and Will which were made by my Uncle in favour of my father don't have any value right?
When once a gift deed is executed (of the self acquired property of your father and uncle) and transfer of property under gift deed is effected by way of donee accepting the gift and getting into possession of the property, the donor cannot unilaterally cancel the gift deed later on without the consent and approval of the donee.
As far as the self acquired property is concerned, I was told by my mother that both property were bought directly in the name of my Father and Uncle (however they both were minor at the time of purchase) but payment was done by my grand mother.