The beauty of selective enforcement. Dig deep enough into your ecclesiastical data-monopoly and you can veto just about any marriage at will. It never was the same again once laymen started to read and write.

Yes, it was the Franciscans who were a huge influence and kept record of these things.

Most people would remember relations as far as great-grandparents and relations to families/family friends that they knew. Literacy was pretty high in the region early on as well, but people continued to rely on the church for recordkeeping.