1. If the deceased member was goverened under the Hindu Succession Act, and has died without making a "will" or a "nomination" for his property THEN "ALL" his legal heir's have an equal share in the property. Tentatively, it would be highly safe for the society to transfer the membership in the name of all the immediate legal heirs of the decease member (i.e. mother + sons + daughters), to safeguard itself against possible future legal disputes.
2. It would be unwise and legally fraught with future projected disputes, if the society transfer the property only in the name of the Mother, irrespective of the fact that all the other legal heirs are giving you an declaration cum affadavit (NOC) in favour of the mother. The society gets embroiled in legal expenses at a latter date, due to the nuisance created by other legal heirs in future.
3. Such declaration cum affadavit has hardly any legal value and can be changed & even disclaimed by the other legal heirs. In such scenario, in legal terms, it is best that all the legal heirs file for Letter of Administration from the competent courts and file their declarations before the judge, who then may issue appropriate orders, which THEN the society may follow safely.
4. The society managing committee is bound to protect interest of its members property and the safest way is to transfer membership of the immediate legal heirs, as explained above.
Keep Smiling .... Hemant Agarwal