Inês was the mistress of Peter (Pedro) I of Portugal. The two became lovers sometime after 1340, but her family ties threatened the interests of the Portuguese monarchy.
So she was incarcerated, then beheaded at a monastery on the orders of Peter's father King Afonso IV, in an attempt to shore up the power of his son's legitimate line.
Inevitably, Pedro took revenge and tore out the hearts of a few of his lover's executioners in 1361. And once he became king, he spawned the creepiest of legends once he declared the dead Inês his lawful wife. Legend says her corpse was exhumed for a bizarre coronation.
p. Pedro Fernández de Castro, Lord of Lemos and Sarria and Aldonça Lourenço de Valadares.
Castro's family came from Galician and Portuguese nobility. She was well connected to the Castilian Royal Family, by illegitimate descent. Her stepmother was Infanta Beatrix of Portugal, youngest dau Afonso of Portugal, Lord of Portalegre and Violante Manuel. Her grandmother was Violante Sánchez de Castile, Lady of Uzero, illegitimate dau of Sancho IV of Castile. Her great-great grandfather was Rodrigo Alfonso de León, Lord of Aliger, illegitimate son of Alfonso IX of León. She was also legitimately descended from Infanta Sancha Henriques of Portugal, dau Henry, Count of Portugal.