 Their first-born daughter Isabella was married to Alfonso of Portugal, and their first-born son John was married to Margaret of Austria.However, the deaths of these children, and the death of Isabella, altered the succession plan forcing Ferdinand to yield the government of Castile to Philip of Habsburg the husband of his second daughter Joanna.In 1502, the members of the Aragonese "Cortes" gathered in Zaragoza, and Parliaments of the Kingdom of Valencia and the Principality of Catalonia in Barcelona, as members of the Crown of Aragon, swore an oath of loyalty to their daughter Joanna as heiress, but Alonso de Aragón, Archbishop of Saragossa, stated firmly that this oath was invalid and did not change the law of succession which could only be done by formal legislation by the "Cortes" with the King.