John II came to power upon his mother's death in 1418. He was now a cousin to the King of Aragon, as Alfonso ascended to the throne upon Ferdinand I's death. John married Maria, the sister of Alfonso V of Aragon. Alfonso himself had already married John's sister, Maria, making the two rulers both cousins and brothers-in-law twice over. John II was now also a cousin and brother-in-law to Alfonso's brothers John and Henry, known collectively as the Infantes of Aragon, who had been given large amounts of land in Castile while their father worked as regent during John II's childhood.