Q : can he sell the property as 4 of his partners are dead ?
No ,since the property is joint so the legal heirs of dead parties can alone sell the property if vaiable .
Q : Does the children of others partners still have any rights ?
Ofcourse the children of dead parties has the right to property of their fathers.
Q : my grandfather has 2 sons will they have to sign on the registration papers ?
All of the legal heirs of the property whether 1 or ten or twenty every one has to sign
Q : if he sells how can a buyer proceed the with legal course as the case is still in progress?
Need to execute GPA and agreement to sell