He also held the viscounties of Marsan, Castelbon, Nébouzan, Villemeur and Lautrec and was, by virtue of the county of Foix, co-prince of Andorra.His maternal grandparents were Charles d'Albret, Constable of France and co-commander of the French army, killed at the Battle of Agincourt, and his wife Marie de Sully.At the time, Eleanor appeared to have few prospects: her father was a younger son and brother of kings of Aragon, and she had two older siblings, Charles and Blanche, standing between herself and the throne of Navarre.However, family dissent and death eliminated both her siblings; Eleanor's father usurped the Navarrese crown, to which he added in 1458 the throne of Aragon (his older brother having died without legitimate children).Following the deaths of Charles and Blanche, King John promised the succession to Navarre to Eleanor and Gaston in return for their loyalty to him, which was given.