[4][2] The earliest mention of Catigern appears in the Historia Brittonum, written in the 9th century and attributed to the monk Nennius.
Chapters 43–45 say that the British king Vortigern had been appeasing the Saxons, and his son Vortimer rose against the enemy and engaged them in four battles.
[5] Chapter 48 also mentions Catigern as Vortigern's second son after Vortimer and before Pascent and Faustus, and reiterates that he died in the same battle as Horsa.
[6] Neither mention is clear as to which side Catigern was on, but context implies he fought alongside his brother against the Saxons.
This Cadell is known from the Historia Brittonum, which says he was a servant who had been converted by Vortigern's enemy Saint Germanus of Auxerre, and thereafter became a king whose descendants ruled Powys through the centuries.
[10] However, one of the genealogies from Jesus College MS 20 refers to a "Cadern", father of Cadell and the son of Vortigern.