Forced Sale of Ancestral Property without the Consent of Legal Heirs

There was a agreed and documented division of the ANCESTRAL properties between the two brothers, with their three sisters giving up (Hakka-sod/ revocation) of their rights. One of the two brothers was my Father who passed away 14 years ago. Only a few months before his death, my father – a heart patient who had already underwent a bypass surgery, was called at the native place by his brother and was forced to give up his share of the ancestral farm lands by pressurizing him with arguments such as he doesn’t have a son (I don’t have a brother, we are only two sisters) and hence why should he share the ancestral property as it would eventually go to his sons in laws. Thus pressurized, he was made to sign a ‘Sales Deed’ of the farm lands in the name of his brother by paying some amount (when in reality, there was no money ever paid). Due to the pressure from my uncle and my grandmother, my father did sign the sales deed which was duly registered. Thus the 7-12 of the land got transferred in the name of my uncle. My father had neither told about this incident to my mother or to both of us sisters (who were already adults then). He told us about this only a couple of months later when he was on the death bed and he realized his mistake. He even wrote a letter of complaint to the Tehsildaar that the sales deed was not as per his full willingness but was under pressure and didn’t have consent from his heirs (i.e. my mother and both us sisters) and hence should be cancelled. However soon enough he passed away. Now my questions to you are, 1. Can we file and win a court case on the basis that the consent of the legal heirs was not obtained during a sale of the ancestral property? 2. Can we take help of the fact that my father actually wrote a complaint letter (we have copies and postal acknowledgements too) that the sales deed was against his will and should be considered invalid. 3. A long period of 14 years is passed since the sales deed/ death of my father. Does this fact weaken our case? Please advise.