Property disputes in society

I have purchased a flat in Mumbai ,we have to much issue in our socitey .our society is newly constructed there are around 50 flats.the land is belongs to collector and he has allocated his land to government employees.26 people came together and registered their society and they given a contract to builder.builder agreed and provided flats to this 26 government employees and purchased tdr and constructed 6 more floor with poper cc and plan approval from BMC.main issue is chair person of the society misused his power by allocating remaining 24 share certicate to some other people and made them members of the society.but those people have only share certificate as a proof of evidence and we are the 24 people who we have purchase flats from builder we have purchase agreement and payments receipt .in this days the 24 people who are holding share certificate are also claiming that this is thier flats. Can a person can become a flat owner without purchase agrement if he only owns share certificate ?