I would prefer you to get a non-availability certificate along with two affidavits from people who were alive when your parents were born. That is what I would recommend. If it is too cumbersome you could try to set up the reciprocity table as evidence if such documents are not available. FAQ in detail...
Note: This is a verbatim transcript of the referenced audio/video media delivered as oral communication, and, therefore, may not conform to written grammatical or syntactical form.