Hi
I am looking for help on marriage certificate too, please let me know if someone has approved format of marriage affidavit ?
Let's clarify the issue: your parents are married, but there is no marriage certificate/impossible to get a replacement?
I don't know the issue in detail but here are options:
-if your parents live together and have for a long time, they can just declare that they are common law.
-if their country allows it, get married now (may not be allowed in some jurisdictions if already considered married).
or,
-do an affidavit. An affidavit is just a letter sworn in front of a lawyer or notary, usually. Form can usually be any form at all: they swear that they were married on [date] in front of [officiant] and have been married ever since in eyes of [local legal system] and never divorced or separated. Official documents not available because [short explanation] and cannot be replaced. [Formal part of the affidavit is completed by lawyer or notary, something like 'sworn in my presence on [date] in evidence of which [signature or seal or something'].
Good luck.