kumarmenon :
1. Since you wish to have complete ownership & title of your fathers property (which is not possible via a nomination), the only viable permanent legal option is file for a "Letter of Administration" (LA) in the competent court.
2. All known and unknown and other claimants will be a issued a court notice (including your mother). The notice also shall be issued to your society, as a interested party.
3. After all have filed in their reply (say) / statement / affadavit / relinqishment wishes etc..., the court, depending on merits, will direct the society to transfer the "ownership & title" of the said property to you (subject to various parameters in your petition)
4. The above decree by the court, will enable you to permanently hold clear "ownership & title" of the said property to you and to your legal heirs in future.
5. A "settlement deed", is a private affair and does not involve other heirs / claimants and further does not give "ownership & title" of the said property. It is further challengable / disputable by other legal heirs / future claimants and such "settlement deed" itself ALSO can be disowned easily by the parties themselves.
6. ANY & ALL other procedures (Nominations, Settlement deeds, etc... ) are always challengable and disputable in a court of law, by various known / unknown future claimants, in the absence of a registered will.
Keep Smiling .... Hemant Agarwal