Transfer and sale of property in gurgaon

With your fathers death certificate your mothers GPA with relevant documents you can change it to your name and afterwards sell it, contact civil advocate.

Your mother shall execute a POA in your favour in the USA.  Then you can sell the property.

This property basically belong to three people, out of which one person is reported to have died intestate.

In order to ascertain the inheritance of his share in the property, a legal heir ship certificate has to be obtained by giving an affidavit duly attested by Indian consulate/Official of Indian embassy of your country, after which you can apply for legal heir ship certifiate in India before the concerned revenue department based on the said affidavit and the death certificate of your father  and copies of the sale deed, revenue taxes receipt and other relevant papers of the property.

After  that your mother can execute a popwer of attorney deed in favor of any close relative who is a resident in India, by getting it duly attested by the Indian consulate or a local notary public, send it to the power agent by sealed cover, who will then present it before the concerened sub sregistrar and get it adjudicated. 

Once the POA is adjudicated, if the buyer is ready then you along with the power agent can sell the property jointly by executing a registered sale deed in favor of the propsecive buyer .

Relinquishment deed executed by your mother at USA will not be considrered as a legally valid document and also a foreign citizen cannot execute a power of attorney deed in favor of another foreign citizen.

You and your mother both are foreign citizens. 

You can consult an experienced lawyer in India where the property is situated and proceed as per further suggestions made. 

Thank you for the detailed replies.

A couple of follow up :

1. Is there a reccomended law firm or good lawyer in the NCR are who can help me with this. I woudl love to hire someone to help.

2. POA :  I am an OCI (US citizien) will that allow my mother to execute POA to me ? I am a little confused as to why a "foreign citizen can sign the actual sale  (if she could travel) but can not grant another foreign person (me) the power of attorny to sign on her behalf ?" as mentioned in the  answer above 

3. For my dad (deceased) I have the US  death certificate and a  copy of his will (when he wrote it in india - signed by 2 others) leaving me his share of the property of which my mother and  I are the legal heirs anyway.

So essentially my hope is to sell this to the buyer I already have in India  by combining these 3 pieces of the puzzle :

1. being present and signing myself ( I am the primary owner of the house registerd)

2. having a POA  or a letter of relinquishment from my mother (if necessary witnessed by indian consulate) - worst case I can get it for another Indian  citizen but not preferred

3. Bringing my dad's death certificate and his will if necessary (my mother by law is also my dad sole heir). this is the one I am most confused about what exactly do we need ?