Son of Constantine and father of Arthurís warriors Geraint, Ermid, and Dywel.

Erbin ruled a Cornish kingdom, which he had to turn over to his son Geraint when he became ill. Geraint returned rule of the land briefly to Erbin when Geraint left for a series of adventures, but he eventually came back and took the crown from his aging and grateful father.

His counterpart in the French romances, as Erecís father, is Lac.