Did the PSK application go through without issues?
The purpose of PVC is to check the applicants status not the parents birth certificates. Are there other legal documents like Aadhar card for your parents that prove the age? If yes start going the legal route – start with an RTI.
See the links below.
https://passportindia.gov.in/AppOnlineProject/online/faqApplicationForm
https://passportindia.gov.in/AppOnlineProject/online/faqPoliceVerification