Rights in property

50 years ago my father got room from housing board on rental basis. later on housing board transfered ownership of said room to my father after payment of rs. 5000/-. five years back that old building was demolished under redevelopment plan, and old society was dissolved and when new society formed father transfered ownership to my mother. Now i found out that my mother didnot mentioned my name in nominee in housing society. she put only my father and sisters name in nomination form. Now my question is can my mother deny my share in that property? as that property is not earned by my mother, currently my father is not owner of that flat as he has transfered ownership rights to mother. can my father or mother make gift deed in fevour of my sister and deny my rights on said property? if will is made and registered, of which i dont have any idea, i am kept in dark. can i challange gift deed or will made by my mother? as she did not earned that property. I dont want to lose my share in that property. Please advise. Thank you.