The Gwentian Chronicle records that "his son Owain took the rule of Ceredigion" after the death of "Hywel the Good, son of Cadell king of all Wales" in 948.
King of Gwynedd, jointly with his brothers. Gerald of Wales´s Descriptio Kambriæ records the descent of the rulers of South Wales in reverse chronological order as follows: “...Theodorus filius Cadelh, Cadelh filius Eneæ, Eneas filius Oenei, Oeneus filius Hoeli da, id est Hoeli boni, Hoelus filius Cadelh, Cadelh filius Roderici magni”.
The Annales Cambriæ record that "Owinus filius Hoeli" died, undated but apparently in 988 from the context. The Chronicle of the Princes of Wales records that "Owain son of Howel" died in 987. 1
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Owain and his two brothers, Rhodri, d. 953, & Edwin, d. 954, were jointly kings of Deheubarth (Seisyllwg and Dyfed). The youngest, Owain, was sole king from 954.
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On Hywel's death in 950 Deheubarth was shared between Owain and his two brothers, Rhodri and Edwin. The sons of Hywel were not able to keep hold of Gwynedd, which was reclaimed for the traditional dynasty of Aberffraw by Iago ap Idwal and Ieuaf ap Idwal, the sons of Idwal Foel.
In 952 Iago and Ieuaf invaded the south, penetrating as far as Dyfed. The sons of Hywel retaliated by invading the north in 954, reaching as far north as the Conwy valley before being defeated in a battle at Llanrwst and being obliged to retreat to Ceredigion.
Rhodri died in 953 and Edwin in 954, leaving Owain to rule Deheubarth alone. Owain did not again try to reclaim Gwynedd, but instead he and his son Einon turned eastwards to attack the kingdom of Morgannwg (modern Glamorgan) in 960, 970 and 977. Owain was now aging, and it appears that Einon took over the rule of the kingdom on behalf of his father. On a further raid on the east in 984, Einon was killed by the noblemen of Gwent.
Following Einon's death, Owain's second son, Maredudd, took over the leadership in war, and in 986 did what his father had failed to do by seizing the throne of Gwynedd, ousting Ieuaf's son Cadwallon ab Ieuaf. The following year Owain died and Maredudd became king of Deheubarth as well as Gwynedd.
The Annales Cambriae were compiled at Owain's instigation. 2
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His name appears as [O]uen map Iguel and[O]uen map Elen merc Louarch (Owain son of Elen daughter of Llywarch) at the head of the old Welsh genealogies of Gwynedd and Dyfed, a text probably compiled early in his reign, thus emphasizing the dual focuses of his inheritance - comprising a kingdom approximating a united Wales - at the time of the death of his father Hywel Dda in 950.... Owain embarked on a policy of consolidation of Deheubarth, focussing mainly on cultural issues such as the writing and collecting of genealogies and annals. His attack on Morgannwg in 960 points to a changed direction of his expansionism from Gwynedd to south-eastern Wales.... 3
General Notes: