Pl advise

I have been staying with my mother along with my wife and a son in Mumbai .In the year 1982 my father died.I was unmarried then and was residing in a tenanted room with my mother and two unmarried younger sisters. At the time of the death of my father ,My elder brother was staying in his ownership flat and elder sister was staying in tenanted property.(Recently elder sister has shifted to ownership flat )The younger sisters who were staying with me at the time of death of my father are now married and have been staying in their ownership accommodations. For the transfer of rent receipt in my name ,my elder brother along with all the sisters and my mother signed duly notarised affidavit by relinquishing their rights in the tenanted room .I had paid Rs 80000/- by way of cheque to my brother as consideration and the mention of cheque payment is indicated in the affidivit The sisters and mother did not ask for money On the basis of affidavit and application letter( to the landlord ) signed by above mentioned relatives for the transfer of tenanted room the landlord transferred the rent receipt in my name and issued rent receipt The above tenanted property was redeveloped in the year 1992 Since the records of Mumbai Mun Corpn and MHADA had my name as a tenant The developer invited me for signing redevelopment agreement and sale deed duly registered with stamp duty .After occupying new room the co op society was formed and share certificate has been issued to me.I am also managing committee member and treasurer of the subject hsg society Nearly 10 days back my elder brother along with elder sister and a sister staying with me at the time of my father's death had written a letter to society stating the society should disallow sale of the flat It was also stated that the above mentioned affidavit signed by them were taken under coercion.One of my sisters and my mother has not signed the subject letter In view of the above please advise me whether my above relatives can stop me selling the flat .If i buy another tenanted room or ownership room,Whether my above relatives can claim share in my existing property .Can my above relatives persuade my mother to file a false suit for harassment. If yes , what would be the consequences Taking cognisance to above letter i had requested to my housing society to send a reply to my relatives stating society does not have any role,my request has been turned down by the society secretary I EARNESTLY REQUEST YOUR ADVISE