Property related

There is a underconstruction building in Kolkata. Total number of flats in this building is 6 of which 3 are landlord part and 3 are developer part. I booked one flat on 12th March, 2019 of developer part. But developer committed suicide on 6th June, 2019. Later on I came to know that against 3 flats of developer part, developer did sale deed agreement with other 8 persons including me. Later on I come to know that expect me all are investors. Most of them deals with half cash and half by bank cheque. For eg. Total cost of one Flat is 26 lakhs. One investor did sale deed agreement against 1 flat with part payment Rs. 16 lakhs of which he paid Rs. 8 Lakhs by cash and rest Rs. 8 lakhs by bank cheuque to the developer. Out of total cost of the flat Rs. 26 lakhs I paid part payment of Rs. 12 Lakhs by bank cheque and I have sale deed agreement, bank statement and money receipt regarding the payment. Now I want to give you some informations that there is a 3 storied building in Dumdum, Kolkata. Present value of the building may be 70 to 80 lakhs.This building is under the ownership of Father of Developer. Developer’s father already expired and present heirs are Developer’s mother, 2 married sisters. Till now partition deed not done between hiers. There is another about 120 sq. ft. office space in another building under the ownership of developer. Present value may be 8 to 9 Lakhs. At present hiers give this space under rent against Rs. 8000/- per month. In this condition can i file court case against heirs and demand to give me money back. Or in this case how Indian Law can support me? In this case is Indian Law is in favour of me. This there any chance of forfeit the money? Pls give me suggestions. Thanks Binod Kumar Dutta