Your sister should execute gift deed for her one third share in property in favour of you and your mother 

2) it has to be stamped  and registered in India 

3) if she is unable to come to India she can execute POA in favour of family member to execute gift deed 

4) POA should be attested before Indian consulate 

 Your sister has to execute a registered Release Deed relinquishing her rights over the share in favour of you and your mother in the jurisdictional Sub Registrar's Office in India. Since you, your sister and your mother are in USA, all of you can authorise someone in India to execute the Release Deed, preferably a blood relative through a POA.

Sitting in USA a deed of gift or relinquishment can not be executed. 

However she can notarise a POA from USA on which basis her constituted Attorney can execute and register such deed in India. 

If your sister desires to relinquish her rights in the property,  she may have to execute a registered release deed relinquishing her rights in the property. 

If she is unable to visit India for executing this registered release deed then she may execute a POA deed in her country of residence   get it notarized by a notary public of that country or get it attested by an official of the Indian embassy and send the deed to the chosen power agent in India. 

The power agent shall get the POA  deed adjudicated before the concerned registrar within whose jurisdiction the property falls. 

After that the power agent can execute the registered release deed on behalf of your sister,  I.e., the principal  to complete the process. 

yyou need to have a legally valid POA. it is mandatorily required to be attested by the Indian Consulate. This is must in order to avoid any issues later in regard to authorization.

The parties will have to execute and register a proper release deed

The release deed has to be prepared by a lawyer. Then stamped for applicable stamp duty in India. Thereafter stamped document has to be couriered to you to the USA. 

In the alternative the children can sign the release deed (without stamp duty) in the USA before the nearest Indian Embassy/Consulate. Or sign it before public notary and obtain certificate of Apostille. 

The children will also make a POA in favour of the mother and sign it in the manner aforesaid. 

Bot the signed documents can then be couriered to your mom in India. Then the applicable stamp duty on both has to be paid within the specified period from the date of first entry of the said documents into India. 

The release deed can then be presented for registration by the Sub Registrar using the POA. 

Signing a simple affidavit by your sister releasing her share before a public notary will NOT suffice because release is a transfer of property which needs to be compulsorily registered

You can ask her to give POA and relinquish deed in front of Indian Embassy and sent here in India for further registeration procedure in respective SRO.

Hi, Your sister has to execute the release deed in favor of your mother and yourself and same has to be registered before the Sub-Registrar office in India. Suppose if your sister not able to travel to India, then she has to execute GPA in favor of yourself or your mother, on the basis of the GPA, you can transfer the property in your name.

You need gi register the same. You need to execute a registered relinquishment deed. It can be done in USA if your sister is there

You need to execute registered relinqueshment deed paying appropriate stamp duty and registration process. 

Hi 

Since it is a relinquishment deed,  it has to be registered at the sub-registrar office where the property is located.

so, the steps are

a)  A relinquishment deed should first be drafted  in accordance to laws with proper description of area, boundaries of property etc and

b) the persons residing in USA should sign the relinquishment deed in presence of officials of Indian Embassy.

c) Thereafter , the persons residing in USA should  also give a signed special power of attorney (again signed and attested in presence of officials of Indian Embassy) and

d) the person holding power of attorney shall  then register the special power of attorney before the Sub-Registrar office after payment of stamp duty and registration charges.

e) Indian embassy officials charge a nominal fee for attestation of documents. you can check the procedure for attestation in Indian embassy / consulate website. 

Hope this information is useful. 

- She can release her share in favour of you and your mother , after executing a registered release deed in India.

- Since , she is unable to come to India for the same , then she can execute a POA in favour of any relative or nearest one in India. 

- The said POA should be attested from the notary in US and further attested from the office of Consulate of India in US.