I am from Bangalore. I dont have a Birth Certificate. How to get a Birth Certificate ?

If the birth is not recorded, the applicant should get a Non-Availability Certificate from the BBMP and documents such as address proof are required in the absence of hospital records. The Non-Availability Certificate is an acknowledgement or endorsement from the authorities stating that the certificate is not available with them. Applicants have to fill a form and submit it to the BBMP authorities, who will then verify the data and issue the acknowledgement.

You have to take this certificate and contact a lawyer. They'll ask you to bring your school passing certifiable, voter ID card etc to prove that your Date of Birth as stated by you. A lawyer files an application in the court and after verification a court order will be issued to issue you a birth certificate.