In his youth he was one of the infantes (princes) of Aragon who took part in the dissensions of Castile during the minority and reign of John II.
For the other members of the royal family there is a separate vault, known as the Panteon de los Infantes, or more familiarly by the dreadfully suggestive name of El Pudridero.
The chief remains of the Spanish heroic epic are some poems on the Cid, on the seven Infantes of Lara, and on Fernán Gonzalez, count of Castile.
The king was surrounded by greedy and unscrupulous nobles, among whom his cousins, the sons of Ferdinand, commonly known as the Infantes (princes) of Aragon, were perhaps the worst.
In 1445 the faction of the nobles allied with Alvaro's main enemies, the Infantes de Aragon, were beaten at Olmedo, and the favourite, who had been constable of Castile and count of Santesteban since 1423, became Grand Master of the military order of Santiago by election of the Knights.
(For the events of his reign see the article Spain: History.) He is the hero of a cantar de gesta which, like all but a very few of the early Spanish songs, like the cantar of Bernardo del Carpio and the Infantes of Lara, exists now only in the fragments incorporated in the chronicle of Alphonso the Wise or in ballad form.