In 1328, Peter’s father, Afonso IV arranged for the marriage of his eldest daughter, Maria, to Alfonso XI of Castile. In 1334, she bore him a son, who ultimately became Peter of Castile. However, Maria returned home to her father in Portugal in 1335 because her royal husband soon after their marriage had begun a long affair with the beautiful and newly widowed Leonor de Guzman, which the Castilian king refused to end. Alfonso’s cousin, Juan Manuel, Prince of Villena, had been rebuffed by the Castilian king in 1327 when the two-year child marriage between his daughter Constanza (granddaughter of James II of Aragon) and Alfonso had been annulled to clear the way for the marriage to Maria. For two years Juan Manuel had waged war against the Castilians, who had kept Constanza hostage, until Bishop John del Campo of Oviedo mediated a peace in 1329.
Enraged by Alfonso’s infidelity and mistreatment of his lawful wife, her father made a new alliance with the powerful Castilian aristocrat. Afonso married his son and heir, Peter, to Constanza, thereby allying himself with Juan Manuel. When Constanza arrived in Portugal in 1340, Inês de Castro, the beautiful and aristocratic daughter of a prominent Galicianfamily (with links albeit through illegitimacy, to the Portuguese and Castilian royal families), accompanied her as her lady-in-waiting.
Peter soon fell in love with Inês, and the two conducted a long love affair that lasted until Inês’s murder in 1355. Constanza died in 1345, weeks after giving birth to Fernando, who eventually became the first of Peter’s sons to succeed him as king of Portugal. The scandal of Peter’s affair with Inês, and its political ramifications, caused Afonso to banish Inês from court after Constanza died. Peter refused to marry any of the princesses his father suggested as a second wife; and the king refused to allow his son to marry Inês as Peter wanted. The two aristocratic lovers began living together in secret. According to the chronicle of Fernão Lopes, during this period, Peter began giving Inês’s brothers, exiles from the Castilian court, important positions in Portugal and they became the heir-apparent’s closest advisors. This alarmed Afonso. He worried that upon his death, civil war could tear the country apart, or the Portuguese throne would fall into Castilian hands, either as Juan Manuel fought to avenge his daughter’s honor, or the de Castro brothers supported their sister. Peter claimed that he had married Inês against his father’s orders. In any event, in 1355, Afonso sent three men to find Inês at the Monastery of Santa Clara-a-Velha in Coimbra, where she was detained, and they decapitated her in front of one of her young children. Enraged, Peter revolted against his father. Afonso defeated his son within a year, but died shortly thereafter, and Peter succeeded to the throne in 1357. The love affair and father-son conflict inspired more than twenty operas and many writers, including: the Portuguese national epic Os Lusíadas by Luís de Camões, the Spanish “Nise lastimosa” and “Nise laureada” (1577) by Jerónimo Bermúdez and ‘Reinar despues de morir’ by Luís Vélez de Guevara, as well as “Inez de Castro” by Mary Russell Mitford and Henry de Montherlant’s French drama La Reine morte.
It was after after the loss Inês he was approached by his grandmother Elizabeth, who told him about Vampires, and told him she was sure Inês was Peter’s Mate.
He agreed to be Turned.