Regarding Property purchase in Refugee Colony Land Property

Hi, There is a property located in refugee colony. The property had an allotment letter issued by GOVT OF WEST BENGAL 10 years ago and a deed of gift. The owner passed away few years back leaving the property undivided. Now the property (Land) has been restructured by a developer with a S+3 building. The developer (as per agreement) holds the entire ground floor and half of the top floor for selling purpose. The rest portion of the building will be of the owners.The developer also holds selling power of attorney. The property had 17 owners, out of which 8 owners will occupy the room, rest 9 owners have been settled with cash by the developer/8 owners and had given NOC. Now one of the 8 owners wants to sell the flat (his part)and by which approaches to me. There is no such registered partition deed of the property. Only they had mutually partitioned the remaining property and having no such written records. Kindly suggest if I purchase one apartment out of this building, will my part will be registered in the GOVT recordsand mutated in the Municipal Corporation? And what is the risk of demanding the property by the heirs/successors of the rest owners in future? Thanks, Kalyan