Piers Gaveston's father was Arnaud de Gabaston, a Gascon knight in the service of Gaston VII of Béarn. Gabaston had come into a substantial amount of land in Gascony through his marriage to Claramonde de Marsan, who was co-heir with her brother of the great landowner Arnaud-Guillaume de Marsan. Through the possessions of his wife, Gabaston also became a vassal of the King of England, in the King's capacity of Duke of Aquitaine. His service to Edward I of England stretched over a long period of time, starting in the Welsh Wars of 1282–83, in which he participated with a substantial contingent. Sometime before 4 February 1287, Claramonde died, and for the rest of his life Gabaston struggled to retain his wife's inheritance from rival claims by relatives and neighbours. Because of this, he became financially dependent on the English king, and was continuously in his service. He was used as a hostage by Edward twice: first in 1288 to Aragon, secondly in 1294 to the French king, when he managed to escape and flee to England in 1297. After returning home, he was back in England in 1300, where he served with Edward I in the Scottish Wars. He died at some point before 18 May 1302.