What Brittonic dialect was spoken in the kingdom who had the father of Owain mab Urien as king?
Owain mab Urien Owain mab Urien (or Owein) (died c. 595) was the son of Urien, king of Rheged c. 590, and fought with his father against the Angles of Bernicia. The historical figure of Owain became incorporated into the Arthurian cycle of legends where he is also known as Ywain, Yvain, Ewain or Uwain. In his legendary guise he is the main character in Chrétien de Troyes's "Yvain, the Knight of the Lion" and the Welsh Romance "Owain, or the Lady of the Fountain", which corresponds to Chrétien's poem.
Arthen ap Seisyll Arthen son of Seisyll (Welsh: "Arthen" or "Arthgen ap Seisyll"; died c. 807) was a king of Ceredigion in Wales of the Early Middle Ages. His father was Seisyll ap Clydog.