A son of King Morvid of Britain who, according to Geoffrey of Monmouth, succeeded his brother Arthgallo to the throne.
He ruled with justice, but he was deposed by his two younger brothers, Iugenius and Peredur, and thrown in prison. After his brothers’ deaths, Elidur was released and given the throne again.
He was succeeded by his nephew Regin. Elidur’s son, Gerontius, eventually became king.
Source
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138