His descendants became high-ranking nobles, imperial officials, and finally kings of Portugal and emperors of Brazil.

Historians believe he was born in Veiros, Estremoz, Alentejo, as a natural son of Portuguese King John I and Inês Peres.

At a meeting of the Portuguese Cortes summoned by Afonso's half-brother John, Lord of Reguengos de Monsaraz, the regency was awarded to the Infante Peter, Duke of Coimbra, another half-brother of Afonso and an uncle of the young king.

It was during this period that the first subsidies for the exploration of the Atlantic Ocean were appropriated under the supervision of Henry the Navigator (another of Afonso's half-brothers).

His first marriage was to Beatriz Pereira de Alvim, on 8 November 1400, with whom he had three children: Afonso married a second time, to his first cousin once removed, Constance of Noronha, daughter of Alfonso Enríquez, Count of Gijón and Noreña (a natural son of Henry II of Castile), and of Isabel of Portugal (a natural daughter of Fernando I of Portugal).