Hywel ap Rhys
Rhys' youngest son.
From A History of Wales by John Davies, London, 2007, p. 103:
"A few months after the death of Rhys [in 1093], the forces of Roger, earl of Shrewsbury, surged from Powys into Ceredigion; they built a castle on the estuary of the river Teifi (Aberteifi--Cardigan) and they continued their way towards the fertile lands of southern Dyfed. There, Roger's son Arnulf seized the cantref of Penfro, where he built Pembroke Castle, one of the greatest of the strongholds of the Normans in Wales. Hywel, Rhys's youngest son, was imprivoned by Arnulf, and Gruffudd, the eldest was taken to Ireland for refuge"