Transfer of flats in society

Sir, My father in law and his nephew own a flat jointly. with understanding it was decided that they will pay the maintainance of society in alternate months. now my father in law is no more.. we have got a relaese deed done in which 4 leagal heirs ( inclding my mother in law and her 3 daughters) have transferred their legal rights to my mother in law. after which we have started the process of transfer of name in society. as i said earlier my father had paid alternate months maintainance till feb but his nephew has not been paying maintainance from almost two years.. means his maintainance is due for a one year if i take alternate month. now for transfer of name in society is saying that we have to clear his part of maintainance too. i need clearification on two points. 1. Is there any socity bylaw which says that to transfer the flat we need to clear the other coowners (50% share) maintenance dues. 2. If we do not go ahead with the society transfer is my mother in law legally the 50% owner of the flat through the release deed throughout the life without doing the transfer in her name in the society. 3. If in future the property is sold how will be the process first the clear the dues name tranfer and then NOC of flat. waiting for ur valuable comments on this as its a complex situation and we need some way out of it.