Page "Uther Pendragon" Paragraph 6

Uther's most prominent appearance in early Welsh tradition can also be found in the Triads, in which he is described as son of Custennin the Blessed, and brother to Emrys Wledig and Custennin the Younger.

Following Custennin the Younger's murder at Gwrtheyrn's hands, Uther and Emrys were exiled to Armorica, and their brother's killer took their kingdom by deceit.

Some time later, Uther and Emrys avenged Custennin by burning Gwrtheyrn to death within his castle.