Generally it's given by court but in some places it's given by collectors office too. Depending on the same it has to be applied

• A self-undertaking affidavit.
• Identity proof of the applicant.like passport , Aadhar card 
• Address Proof of all legal heirs like ration card , passport 
• Date of Birth Proof of all legal heirs.
• Death certificate of the deceased person.
• Death certificate of the deceased direct legal heir.
• Residence Proof of the deceased.

you can visit taluka / tehsildar office and obtain application form if you are unable to do it online 

You can get the legal heirship certificate for the legal heirs of the deceased who is reported to have died in that place where he resided for more than a year prior to his death. 

If you are a OCI, then you can ask the other resident legal heirs to apply for the same by producing their AADHAR card. 

If you are the only legal heir,  then you can apply directly to the Tehsildar stating that the eseva service cannot be availed in the absence of AADHAR card or any other identity card .

If you don't have local address then the verification process will be difficult for the authorities concerned hence your application may be rejected. 

In that case you may have to file a suit for declaration to declare you as a legal heir to the deceased before a court competent. 

Dear Sir/Ma'am

You can obtain the legal heir's certificate from Tehsildar's office.

Documents like your Aadhaar, Passport, Address proof and Birth certificate as well as residence proof and death certificate of the deceased will be necessary.

It will be much easier for a legal heir living nearby in Tamil Nadu to obtain the same than it will be for you.

Thank you

- For getting legal heirs , you can apply before the Tehsildar of your area after submitting the death certificate of deceased including the details of all legal heirs .

- Since, you not having adhar card , then other members can apply online from his Aadhar card , and your passport etc. will be a proof of that you are the legal heir of the deceased. 

- If you are only one and not other legal heirs alive , then you will have to apply directly with the help of any relative or nearest one in India.