Apply for a certified copy in the registrar's office and then apply for succession certificate in the court,take a GPA from the sibling who is not interested in his share.

you may follow the guidelines of Mr. Rohini

For inheritance or succession, no documentation is necessary.

Obtain certified copies of documents of ownership from registrar's office as also copies of the concerned revenue records like Patta, Property Register Card, Municipal Record etc. Submit an application and affidavit for recording of names of heirs in place of deceased owner with his/her death certificate.

You may draw a family settlement incorporating a clause that one of the siblings has relinquished his share in favour of the remaining two in lieu of other assets. Based on this family settlement you may approach the authorities for mutation of your name in the records of ownership.