rival Giuliano della Rovere) Pope Sixtus IV. Della Rovere's appeal was that he was a pious and brilliant Franciscan monk who lacked many political connections in Rome. He seemed to be the perfect cardinal to reform the Church, and the perfect cardinal for Borgia to maintain his influence. Sixtus IV rewarded Borgia for his support by promoting him to cardinal-bishop and consecrating him as the Cardinal-Bishop of Albano, requiring Borgia's ordination as a priest. Borgia also received a lucrative abbey from the pope and remained vice-chancellor. At the end of the year, the pope appointed Borgia to be the papal legate for Spain to negotiate a peace treaty between Castile and Aragon and to solicit their support for another crusade. In 1472, Borgia was appointed to be the papal chamberlain until his departure to Spain. Borgia arrived in his native Aragon in the summer, reuniting with family and meeting with King Juan II and Prince Ferdinand. The pope gave Cardinal Borgia discretion over whether to give dispensation for Ferdinand's marriage to his first cousin Isabella of Castile, and Borgia decided in favour of approving the marriage. The couple named Borgia to be the godfather of their first son in recognition of this decision. The marriage of Ferdinand and Isabella was critical in the unification of Castile and Aragon into Spain. Borgia also negotiated peace between Castile and Aragon and an end to the civil wars in the latter Kingdom, gaining the favour of the future King Ferdinand who would go on to promote the interests of the Borgia family in Aragon. Borgia returned to Rome the following year, narrowly surviving a storm that sunk a nearby galley that was carrying 200 men of the Borgia household. Back in Rome, Borgia began his affair with Vannozza dei Cattenei which would yield four children: Cesare in 1475, Giovanni in 1474 or 1476, Lucrezia in 1480, and Gioffre in 1482. In 1476, Pope Sixtus appointed Borgia to be the cardinal-bishop of Porto. In 1480, the pope legitimized Cesare as a favour to Cardinal Borgia, and in 1482, the pope began to appoint the seven-year-old to church positions, demonstrating Borgia's intention to use his influence to promote his children. Contemporaneously, Borgia continued to add to his list of benefices, becoming the wealthiest cardinal by 1483. He also become Dean of the College of Cardinals in that year. In 1484, Pope Sixtus IV died, necessitating