Juan Manuel, Prince of Villena
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.