The future of the House of Avis seemed assured by the presence of João's five legitimate sons, but the king also provided for his illegitimate children as he had been provided for by his father. João conferred on his bastard son Afonso the hereditary title of duke of Bragança and endowed him with lands and properties that amounted to the creation of a state within a state supported by a huge reserve of armed retainers. The House of Bragança accumulated wealth to rival that of the crown and eventually assumed the leadership of the old aristocracy in opposition to Avis.

When João I died in 1433, the crown was assumed by his eldest son, Duarte, who died five years later of the plague. Before his death, Duarte convoked a cortes in order to legitimate the compilation of Portuguese royal law, but the work was not completed until the reign of his son, Afonso, and is, therefore, named the Afonsine Ordinances. He also declared that the grants of land so lavishly awarded by his father to his supporters would have to be confirmed, as was the custom at the start of each reign.

Afonso was six years old when his father died and his mother, Queen Leonor of Aragon, assumed the regency. There was opposition to the assumption of all authority by a woman, and Leonor agreed that Duarte's brother, Pedro, should become regent. This was opposed by Afonso, duke of Bragança, the eldest illegitimate son of João I. Both men aspired to gain influence over the young king by marrying him to their daughters. The populace of Lisbon strongly favored Pedro and acknowledged him as regent. Pedro received confirmation for his regency by summoning the cortes at Évora and paved the way for his continuance in power by arranging the marriage of his daughter Isabel to the young king, who, when he reached his majority in 1446, agreed to the match and asked his uncle to continue the regency.

The duke of Bragança reasserted his ambitions and was able to influence the young king to dismiss Pedro by convincing him that his uncle was plotting to seize the throne. Pedro was banished to his estates. When rumors of a plot against him surfaced, he decided to resist and marched on Lisbon, where he had the support of the populace. Pedro was met by the troops of the king and the duke of Bragança at the Battle of Alfarrobeira on May 24, 1449, where he was killed and his army defeated. This battle resulted in the enlargement of the property and wealth of the illegitimate line of the House of Avis, which allowed it to enjoy enormous influence over the pliable Afonso V until his death in 1481.

Data as of January 1993