Gruffydd was the son of Rhydderch ab Iestyn who had been able to take over the kingdom of Deheubarth from 1023 to 1033.
He was said to be a powerful king who stoutly resisted raids by the Danes and attacks by Gruffydd ap Llywelyn.
In 1055 however Gruffydd ap Llywelyn killed him in battle and recaptured Deheubarth.
In 1049 he is reported raiding up the River Severn in alliance with an Irish Viking Fleet.
[2] His son Caradog ap Gruffydd (who received Caerleon in 1057[1]) also attempted to emulate his father and grandfather by gaining control of Deheubarth but was killed at the Battle of Mynydd Carn.