Caderyn Fendigaid ap Gwrtheyrn, Brenin Powys - Father

I Googled and see that his Wikipedia page doesn't have a surname for him. It just has his as Catigern 'the Blessed' and does say he is tradtionally believed to be the son of Vortigen.

Maybe it would be less confusing if his profile here left the surname off as well since it doesn't 'fit' with who his father is believed to be. ?

https://en.wikipedia.org/wiki/Catigern

Ah-ha! I was reading the lengthy notes in his father's About section and found this:

"...Vortigern, whose real name was thought to be Gwrtheyrn but, as was the custom in those days, was known by a description and became Vortigern Vorteneu meaning ‘High King – The Thin’ "

So that explains where the ap Gwrtheryrn came from, which I still find confusing for anyone just looking at the names and seeing that Caderyn's surname doesn't follow tradition. I guess when his dad changed his name, the change didn't trickle down the line.