Wikipedia
Penychen was a possible minor kingdom of early medieval Wales and later a cantref of the Kingdom of Morgannwg. Penychen was one of three cantrefs that made up the kingdom of Glywysing, the other two being Gwynllwg and Gorfynydd. The cantrefi were created on the death of Glywys (c.480 AD), the first king of Glywysing, when the kingdom was divided between three of his sons, Pawl, Gwynllyw and Mechwyn. Pawl was the ruler of Penychen and on his death (c.540 AD) passed the cantref onto his nephew.
Pawl's brother Gwynllyw was the ruler of Gwynllwg and upon his death the cantref passed to his son Cadoc (Cadwg), also known as St. Cadoc. Cadoc would later take control of Penychen, but when he was killed by the Saxons he had no heirs and the both cantrefi fell under the control of Meureg of Gwent and both were absorbed into his kingdom.