1) on aunt demise your father was nominee and only legal heir .

2) I presume aunt was unmarried

3) on father demise you and your mother are the legal heirs

4) apply to society to transfer share certificate in your and mother name

5) society may agree to do so on furnishing indemnity bond to indemnify society against claims made if any

6) society may also direct issue of public notice

7) you can execute relinquishment deed to relinquish your share in property then flat would be transferred in mother name

If society insists to obtain court order the you have to apply for and obtain letters of administration from district court

1) relinquishment deed or gift deed is to relinquish / transfer your 50 per cent share in property

2) relinquishment deed or gift deed has to be duly stamped and registered

3) stamp duty would be 2 per cent of market value of your share in property

Relinquishment deed means that one person relinquishes his or her share of property in the name of some other person.

You may contact a local lawyer for the same.

Regards

This property was in the name of yor paternal aunt.

If she was married and died intestate this property on her name shall devolve on her own legal heirs namely her husband and children.

If she was unmarried and died intestate then this property shall devolve on her class I legal heirs consisting her mother.

If her mother was not alive during her death, then the property will devolve on her class II legal heirs, i.e., your father and all other siblings.

If there were no other class II legal heirs other than your father then the property devolved on your father and subsequent to his intestate death the same again devolved on his own legal heirs consisting your mother, yourself and your siblings.

Since you state that you are the only child to yor parents you can give NOC for transfer of this property to yor mother's name and your mother after acquiring the share certificate on her name from the society by fulfilling the other necessary formalities, can nominate you as her nominee.

You can execute a registered release deed in your mother's favor so that she becomes the absolute owner of the property by title.

Additional Information - Property is occupied since 30 years by me and my family.

You have not furnished the details of the legal heirs of your paternal ant nor her marital status at the time of her death

Also, What is a Relinquishment Deed how to get it done and how much will be the charges for same? Whom should we contact for this process?

Since you have already initiated the process of transferring the property in yor mother's name in the society, there is another process to be done for transferring the property to or mother's name by executing as registered release deed relinquishing your rights in the property in her favor.

For this yo may contact a local document writer, who will prepare a registered release deed accordingly, get the same executed before the concerned registrar's office which will confer the title on your mother's name.

The fee and other formal procedure may be enquired locally