Álvaro Pires de Castro

Álvaro Pires de Castro (c. 1310 – 11 June 1384 in Lisbon) was a powerful Galician-Portuguese nobleman, stem of the Portuguese branch of the House of Castro. He was the first Count of Viana (da Foz do Lima), the first Count of Arraiolos and the first Constable of Portugal.

Álvaro Pires de Castro (sometimes written as "Peres de Castro" or "Pérez de Castro") was the illegitimate son of the powerful Galician nobleman Pedro Fernández de Castro and his mistress Aldonza Lorenzo de Valladares. As a result, he was the half-brother of the powerful Galician nobleman Fernando Ruiz de Castro, the Castilian queen Juana de Castro (wife of King Peter of Castile) and a full brother of the controversial Inês de Castro, mistress and consort of King Peter I of Portugal.

The Galician Castro family had strong connections to the Kingdom of Portugal, to which they were intermittently exiled. Inês de Castro came to Portugal in 1340, in the capacity of a maid to Constanza Manuel. But Constanza's husband, Infante Peter, fell in love with the young Inês, and carried on openly with her, much to the scandal of the Portuguese court. Peter's father, King Afonso IV of Portugal had tried to banish her, but to no avail. Inês brother, Álvaro Pires de Castro, came to Portugal sometime in the 1340s, and ingratiated himself in the company of Infante Peter. The influence of Álvaro and other exiled Galician-Castilian nobles upon Infante Peter alarmed Afonso IV, who feared they might drag Portugal into the internal quarrels of neighboring Castile, part of which were orchestrated by their half-brother Fernando Ruiz de Castro. At length, when it became clear that the Castros were pushing Infante Peter to declare himself pretender to the throne of Castile-León, Afonso IV authorized the assassination of Inês de Castro in 1355.

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