Gruffydd ap Llywelyn Fawr
As a boy, Gruffydd was one of the hostages taken by King John of England as a pledge for his father's continued good faith. On his father's death in 1240 he would under Welsh law have been entitled to consideration as his father's successor. Llywelyn however had excluded him from the succession and had declared Dafydd, his son by his wife Joan, to be heir to the kingdom. Llywelyn went to considerable lengths to strengthen Dafydd's position, probably aware that there would be considerable Welsh support for Gruffydd against the half-English Dafydd.
Gruffydd was held a prisoner by his brother Dafydd when the latter took over Gwynedd. Following a successful invasion of the Welsh borders by King Henry III of England in 1241, Dafydd was obliged to hand over Gruffydd into the king's custody whence he was taken to London and imprisoned in the Tower of London. Gruffydd's wife, Senena (possibly a daughter of Caradoc ap Thomas of Anglesey), agreed to pay Henry 600 marks for the release of her husband and their eldest son, Owain, and to hand over her two youngest sons, Dafydd and Rhodri, to the king as hostages to ensure that she kept her part of the bargain. Henry did not keep his part however, and kept Gruffydd and his son imprisoned as "guests" because this continued to give him the possibility of using Gruffydd as a weapon against his brother.
However, Gruffydd died while attempting to escape from the Tower in 1244. He is said to have used an improvised rope made from sheets and cloths to lower himself from his window, but as he was a heavy man, the rope broke and he fell to his death.
After his death Gruffydd's four sons—Owain, Llywelyn, Dafydd and Rhodri—would come into their own, and after much fraternal discord, Llywelyn ended up ruling most of Wales. He also had three daughters, Gwladus, Catherine and Margred.