Transfer of Ownership of residential flat

My flat which I am staying in was brought by my dad's unmarried sister and my dad was one of the nominees of the flat along with his elder sister residing in Australia and his sister in law (deceased brother's wife). Owner of flat which is my dad's younger unmarried sister passed away without will. My dad, his elder sister are also no more. Flat is still on original owner (my dad's younger sister) and we have been occupying since her death and paying all maintenance. Now society is going for redevelopment and my dad's sister in law who is in US is not in touch with us. Also dad's elder sisters son in in Australia and is also not in touch. How do we get our right in the flat from builder since both other nominees are not concerned and not in touch with society. However, my dad's sis in law had at the time of my dad's younger sisters death submitted a letter to society that my dad, his deceased elder sister's son and herself will submit transfer papers to get flat title of ownership transferred but which never happened. This was 8 years ago.