On his death in 949 his sons were able to keep control of Deheubarth but lost Gwynedd to the traditional dynasty of this kingdom.
Hywel Dda unites the kingdoms of Dyfed and Seisyllwg to create Deheubarth.
Anarawd ap Gruffydd (died 1143) a prince of Deheubarth in south-west Wales.
The FitzGerald dynasty and related families of Ireland are female line descendants of the Welsh royal family through Nest, daughter of Rhys ap Tewdwr, last King of Deheubarth, whose descendants include Elizabeth I, John F. Kennedy, and Diana Princess of Wales.
Hyfaidd's sons Llywarch and Rhodri reigned after him, but the kingdom was soon lost to Cadell's son Hywel who consolidated his realms as Deheubarth.
Llywelyn traced his ancestry to Sandde, a different son of Llywarch Hen from that claimed by the kings of Gwynedd and Deheubarth.
Maelgwn ap Rhys (c. 1170 - 1230), son of Rhys ap Gruffydd and ruler of part of Deheubarth
Owain ap Hywel Dda or Owain ap Hywel ap Cadell, a 10th-century king of Deheubarth
Rhys Gryg – fourth son of Rhys ap Gruffydd (The Lord Rhys) – of Deheubarth occupied the peninsula in 1215, but in 1220 he ceded the area to the English, apparently on the orders of Llywelyn ap Iorwerth.
The Welsh Bruts state that "Rhys ap Tewdwr, king of Deheubarth, was slain by the Frenchmen who were inhabiting Brycheiniog."