Cadwaladr ap Gruffydd was Owain Gwynedd’s brother. A royal family in Wales wasn’t the same as in England, where the eldest son inherited most everything. In Wales, upon the death of a king, an entire kingdom was to be split among the brothers, even the illegitimate ones. (yes, the Catholic Church objected to this, but the Welsh didn’t much care). This caused problems for Wales time and again–as the brothers fought over lands among themselves and what had been a united kingdom under the father became divided under the sons.
Cadwaladr and Owain were often at odds. Owain became the eldest son when his brother, Cadwallon, died, leaving Owain and Cadwaladr to rule without him.
Owain and Cadwaladr seemed to have split their territory amicably at first, but in 1143 AD, “Cadwaladr’s men killed Anarawd ap Gruffydd of Deheubarth by treachery, apparently on Cadwaladr’s orders.” Anarawd was the King of Deheubarth, in fact, and this was on the eve of his wedding to Owain’s daughter. This marriage would have united the two kingdoms of Gwynedd and Deheubarth. And Cadwaladr has Anarawd murdered!
Owain Gwynedd “responded by sending his son Hywel ab Owain Gwynedd to deprive Cadwaladr of his lands in Ceredigion.” Ceredigion just happens to be the lands adjacent to Deheubarth. Did Cadwaladr think that with Anarawd dead, he could pull a land grab? Did he plot with Anarawd’s younger brother? We’ll never know.
“Cadwaladr fled to Ireland where he hired a fleet from the Danish settlement in Dublin and landed at Abermenai in 1144 in an attempt to force Owain to return his lands. Cadwaladr apparently abandoned or escaped from his allies and made peace with his brother, who obliged the Danes to leave.” http://en.wikipedia.org/wiki/Cadwaladr_ap_Gruffydd
Things remained uneasy between the brothers for the rest of their lives. In 1147, the brothers fought again, resulting in Cadwaladr’s loss of Meirionydd. Their animosity was further exacerbated by the fact that Cadwaladr sided with King Henry II in 1157 AD when he invaded Wales. Cadwaladr, through his marriage to Alice Fitz Gilbert, had become a land owner in Lancashire and Shropshire. http://www.red-dragon-wales.com/WelshPrinces/OwainGwynedd_1.htm
That war resulted in a stalemate, with Owain giving homage to Henry and Cadwaladr receiving some of his lands back, but with no real gains by Henry into Owain’s territory. In the end, Cadwaladr outlived Owain but didn’t again attempt to share power with him again.
As a side note, and if you were thinking that this was an isolated incident. The relationship between Cadwaladr and Owain bears a striking resemblance to that of Llywelyn ap Gruffydd and his brothers, Owain and Dafydd. Llywelyn kept Owain in prison for most of his natural life so he couldn’t incite against him, and Dafydd not only defected to the English twice in order to support the English king against Llywelyn, but tried to have him murdered. Read more here: https://www.sarahwoodbury.com/the-brothers-gwynedd/ https://www.sarahwoodbury.com/llywelyn-ap-gruffydd/