 Rhodri's second son Cadell ap Rhodri, however, looked outside Gwynedd's traditional borders and took possession of the Early Medieval Kingdom of Dyfed by the late 9th century, establishing his capital at the citadel of Dinefwr.Cadell ap Rhodri's descendants are designated "Dinefwr" after the citadel from which they would rule Dyfed.The Dinefwr dynasty under king Hywel Dda would unite Dyfed and Seisyllwg into the kingdom of Deheubarth in the early 10th century.