Gwenddoleu ap Ceidio was killed by the joint kings of Efrog in battle in 573 and was possibly succeeded by his brother.
Little is known of his reign, but it ended when, as described in the Annales Cambriae, the sons of Eliffer, Peredur and Gwrgi, the joint kings of Efrog, killed him at the Battle of Arfderydd in 573. It is possible he was succeeded by one of his brothers. 
