CynfynKing Cynfyn was the King of Ergyng, a kingdom of south-east Wales in the early medieval period. He was the son of Peibio Clafrog.LifeLittle is known of Cynfyn ap Peibio apart from the evidence of later medieval genealogies. He appears a number of times in the Llandaff Charters, particularly in association with Bishop Aeddan and Bishop Elwystl.