Not knowing parents birth place

We only knew the birth countries of both our fathers and the registry had no issue with this. We also only knew the countries/provinces for our mothers and again no issue.

It's for the government to verify your identity when you apply for your marriage license. Are they available for you to ask? If not, any other family who would know?

Its a requirement as I had to fill out both our parents birth places. It would be good to see their passports if they have them handy and know from there.