Davydd ap Gruffudd
Source: Wikipedia - Llywelyn the Great
From "Dafydd Goch ap Dafydd - His Real Ancestry" by Darrell Wolcott (http://www.ancientwalesstudies.org/id51.html):
"The intentions of King Edward I in 1283 seem clear enough; he was intent on total extermination of the Gwynedd princely family which had long resisted his authority over Wales. When Llewelyn ap Gruffudd was finally killed in Brecon, his brother Dafydd had taken up the fallen crown. While he had a few diehard supporters with whose assistance he tried to continue resistance to the English army, many former allies of his brother had lost their will to pursue what they now saw as a losing cause. When Castell y Bere in Meirionydd, where many believe Dafydd had planned his last stand, was surrendered without a fight in April of 1283, Dafydd went into hiding. He was finally captured in late June, his location betrayed by a cleric, Iorwereth of Llan-faes. His youngest son, Owain, was taken in his father [in late June 1283]. About a week later, his eldest son Llewelyn was found and both boys were taken to the prison in Bristol. Not finished yet, the king sent the young unmarried daughters of both Llewelyn the Last and Dafydd ap Gruffudd to involuntary seclusion for training as nuns. Gwenllian ferch Llewelyn ap Gruffudd was sent to the Gilbertine nunnery at Sempringham, while the unnamed daughter or daughters of Dafydd ap Grufudd were sent to the priory at Sixhills. This insured they would never bear sons to become a future problem for the crown of England; the family had thus been made extinct."