Nothing much is known about the saint himself. Attempts to link him genealogically to other Welsh saints are either anemic imitations of the scriptural genealogies or they are tasteless jokes about Welsh in-breeding. Hard to know which, but I don't put any stock in them either way.
Here's where I am giving credence: you don't dis a Welsh saint. Some English nobleman who was hunting Welsh game (probably peasants instead of pheasants) decided that the St. Afan Parish Church would be the a decent place to bed down with his dogs for the night. (No, I'm not going to write what you're thinking. Not even I am going to be that rude in blog about saints.) When he woke in the morning, his dogs were mad and he was blind. He only recovered his sight by swearing to go on a Crusade. The dogs, alas, could do nothing to recover their wits.