Cancellation of unconditional Gift Deed

Hello Sir, I am from Karnataka. My grandfather have 3 Sons & one Daughter My Grand Father Gifted a self acquired Property to my father (1st Son) in Feb-2000, without any conditions on it & the said Gift was executed by my G.father with love & affection on my father & the Gife was accepted by my father. My grandfather made a gift deed by registered Gift deed, in a Registrar office, by paying all charges. and in the Gift deed, he clearly mentioned that, From now, you are the owner of this property and from now you have all rights on this property and he is giving it with love and there are No conditions in it. Now the EC shows my father’s name in it. Later, my father took some loan from a Bank on that property. Further my Grand Father Gifted one more self acquired Property to his 2nd Son & one more self acquired property to his only Daughter with No conditions on it. Which we never questioned & we don’t have any interest in other Property Now in March 2014 the problem started by the 3rd Son (My Uncle) he has filed a suit on My Grandfather & making all his brothers & sister a party. But have Asking for the cancellation of only the first Gift Deed which is gifted to the first son (MY Father) & he have not asked or questioned for the 2nd & 3rd Gift deeds given to other 2 parties. We were shocked to know that Both My Uncle & My Grand Father wanted the only first Gift deed to be cancelled which was gifted to my father & We came to know that my father’s brother convinced my Grandfather to cancel that deed. Now, we are in big problem to clear the load on that property. And now we want to sell the said property. But there is a court case on the said property so we could not sell the property What is the solution? I heard that the gift deed once made cannot be cancelled on any reason. Can any one help us to educate me on this issue. You are my God, at this point of time. Please help us to know what we can do to get the out of this problem. My Email Id is