In my book, The Good Knight, the King of Deheubarth, Anarawd, dies in the opening chapter.  This is in 1143 AD, and King Owain of Gwynedd rules Gwynedd–and much of the rest of Wales–with a strong hand.

After Anarawd’s death, the rule of Deheubarth falls to his younger brother, Cadell.  “Cadell’s career was effectively ended in 1151. When out hunting, he was attacked by a Norman force from Tenby, who left him assuming him to be dead. In fact he survived, but was so badly injured as to be unable to resume his activities. In 1153 he left on a pilgrimage to Rome, leaving the rule of Deheubarth to his younger brothers Maredudd and Rhys. Cadell is not heard of again until 1175, when he entered the abbey of Strata Florida after a long illness and died there.” http://en.wikipedia.org/wiki/Cadell_ap_Gruffydd

The bastard son of Owain Gwynedd, Hywel, plays a key role in my medieval mysteries.  While Cadell and Rhys are ruling the rest of Deheubarth, Hywel rules Ceredigion, a northern territory carved out of Deheubarth.  However, “Maredudd and Rhys were able to drive Hywel ab Owain Gwynedd from Ceredigion by 1153. The same year, Rhys is recorded as an independent commander for the first time, leading an army to capture the Norman castle of St Clears.  Maredudd and Rhys also destroyed the castles at Tenby and Aberafan that year. Maredudd died in 1155 at the age of twenty-five and left Rhys as ruler of Deheubarth. Around this time he married Gwenllian ferch Madog, daughter of Madog ap Maredudd, prince of Powys.”  http://en.wikipedia.org/wiki/Rhys_ap_Gruffydd

Rhys then began strengthening his position, but realized that he would have to come to an accommodation with King Henry (the war between King Stephen and Empress Maud having finally ended).  “Between 1158 and 1165 Rhys was under heavy pressure from Henry II. He was persuaded to submit, despite the loss of territory involved when Ceredigion and Cantref Bychan were restored to their Norman lords. Immediate retaliation by Rhys and his kinsmen, an attempt to take Carmarthen in 1159, and a successful attack on Llandovery in 1162 pointed for Henry II a recurrent danger: the Welsh prince would not accept an enhanced Anglo-Norman presence in West Wales. For Rhys, submission and defiance were part of the dynamic border conflict.

While Henry lived, Rhys was a trusted agent and ally. For his part, Rhys was content to make the most of his relationship with the king, but he continued to think and act as an independent Welsh prince. He rebuilt Cardigan Castle for his own use, and he used marriage alliances to consolidate his position. As the 12th century drew to a close, Rhys was once again engaged in campaigning against the crown and the greater lords of the southern march, and at the same time he was deeply implicated in internal feuds among his kindred. These struggles presaged the decline of his dynasty and the eclipse of his kingdom. By the time of his death in 1197 he had been an active participant in war and politics for sixty years, and he had been the dominate ruling prince in Wales for more than forty years.”  http://www.castlewales.com/lrdrhys.html

King Owain of Gwynedd died in 1170 and his son Dafydd eliminated all of his brothers over the course of four years, resulting in his undisputed rule of Gwynedd.  He was not a strong king in the way his father had been, with the result that Lord Rhys was the strongest ruler of Wales.  Upon Rhys’ death in 1197, however, Gwynedd again gained the ascendancy with the overthrow of Dafydd by Llywelyn ap Iorwerth, grandson to Owain Gwynedd and his eldest legitimate grandchild.