did your father leave any nomination form ?any will ?
2) apply to society to transfer father 50 per cent share of flat in your mother name on basis of nomination form given by your father to society . furnish your NOC
3) if father did not leave any nomination for his share in flat apply for and obtain letters of administration from bombay high court
4) you can file your consent affidavit to issue LA in mother name
5) if father left a will apply for probate of father will
6) then apply to society to transfer father share of property in mother name