Gruffydd ap Gwenwynwyn was a contemporary of Llywelyn ap Gruffydd, the last Prince of Wales who died in 1282. He was father to Owain, who with Dafydd ap Gruffydd, Llywelyn’s brother, conspired to murder Llywelyn in 1274.
Gruffydd was born sometime before 1216, the date of his father’s death. Llywelyn Fawr had driven the family from their lands in Powys and Gruffydd subsequently grew up in England. “Gwenwynwyn seized Arwystli in 1197 when he was aligned with England. Following the marriage of Llywelyn Fawr and Joan of England in 1208, warfare broke out once more between Gwenwynwyn and Llywelyn. In 1212 Gwenwynwyn’s ancient royal seat at Mathrafal was destroyed and he was evicted from his territories. He changed allegiances again and was restored to his realm in 1215 making a new capital at Welshpool. In 1216 he was defeated in battle with the forces of Llywelyn and fled to England, where he died shortly afterwards.” http://www.welshicons.org.uk/html/powys_wenwynwyn.php
Gruffydd became the ostensible ruler of Powys, but in fact spent most of his life in England, under the patronage of the English kings. He returned to Wales for the first time in 1241, after Llywelyn Fawr’s death, and ruled his principality of Powys-Wenwynwyn off and on, depending upon whether or not Edward or Llywelyn was in the ascendancy, until his death in 1286. His support for the English kings never wavered, and upon Llywelyn ap Gruffydd’s death in 1282, his family became Marcher lords, and changed their name to de la Pole. http://en.wikipedia.org/wiki/Gruffydd_ap_Gwenwynwyn
Of that fateful year of 1274, J. Beverly Smith writes: “before the year was out the two men [Dafydd ap Llywelyn and Gruffydd ap Gwenwynwyn] who had conspired to put the prince to death had found refuge in England by the king’s permission. The decision to allow them sanctuary in the king’s realm made a fundamental difference to relations between king and prince . . . Dafydd, pressing the king for support, asked for guidance as to how he could do most to damage Llywelyn . . . [in a letter] Llywelyn told how the men of Gruffydd ap Gwenwynwyn had come from the safety of their retreat in Shropshire to attack Powys Wenwynwyn. They had come six times and audaciously sold the booty at the markets of Shrewsbury and Montgomery. One of the prince’s men had been decapitated in public . . .” (Llywelyn ap Gruffydd p. 383).
The name ‘Gwenwynwyn’ is a triple repitition of “wyn” which means “white, fair, or blessed”. http://www.behindthename.com/name/wyn
or, possibly something along the lines of “land of the white lambs” since “wyn” in my modern Welsh dictionary means ‘lamb’.