Cancellation of saledeed

Dear sir, My father hs alloted a plot of 1800 sq feet by a housing society in 1982. & it was in my father's possesion till last month, march 2017. on that plot there was a temporary tin-shade, where my father has placed a renter. This property was under disput and a suit was filled by plaintiff in district civil court in 2007 for 'recovery of possession' & 'decleration of title' and is pending till the date. In that suit my father and the renter was respondent no.1 & 2 respectively. In 2013. the plaintiff sold the property to another person who recides becide the plot at his own house adjacent to the boundries of the disputed property ( point to be noted that the Bayer was awared about the disput of the property.) with a sale-deed made at sub- registrar's office. After which in last month of 2017, The Bayer forcefully evacuated the plot, and totally broke the tin-shade. saying that, the property belongs to him and also submitted a caveat against my father for T.I. Now, If my father's lawyer did not demanded T.I. in past in the suit filled by plaintiff in 2007. is it possibble for us to cancel this sale-deed? If yes how? & If no, why ?