The kings of Glywysing were descended from King Arthur as indicated by JC20 12:
|Gen.||JC20 12a seg.|
Morgan Hen died in the year 974. The LL tells us:
Morgan Hen son of Owain, King of Glamorgan, contemporary with Edgar, King of England …
Edgar died a year later in 975. The father of Morgan, Owain, according to the ASC, accepted Athelstan as overlord in the year 926. Arthfael’s father is given by JC 9 as Gwriad ap Brochwel. His mother, Ceingar from Dyfed.
 Rees, W. J., 1840, 502