Throughout 1476, supporters of Joanna from the nobility continued to submit to Isabella and Ferdinand, particularly those from the Pacheco-Girón lineage: Juan Téllez-Girón and his brother Rodrigo; Luis de Portocarrero; and, in September, the Marquis of Villena. In November 1476, Isabella's troops captured the castle of Toro. In the following months, they  took control of the last bordering localities controlled by the Portuguese and dealt with their adversaries in Extremadura. In July 1477, Isabella arrived in Seville, the most populous city of Castile, with the objective of asserting her power over the nobility of Andalusia. In April 1476, Isabella and Ferdinand gave their first exculpation to the Marquis of Cadiz. He had been regaining power while his rival, the Duke of Medina Sidonia, initially the main Isabella supporter in Andalusia, had been falling into dishonour. Through skilful negotiations, the Queen managed to take control of the main strongholds of Seville occupied by the Marquis and the Duke and, instead of returning them to their legitimate owners, named others as their heads. She prohibited both nobles from entering the city of Seville, under the pretext that their simultaneous presence there would risk violent conflicts. In this way the Duke's political dominance over Seville disappeared, and the city passed into the control of the Crown. One of the few nobles that refused to submit to the monarchs was Marshall Fernán Arias de Saavedra. Isabella's troops laid siege to his fortress at Utrera, and conquered it by assault in March 1478. The defeated suffered harsh repression. The first son of the monarchs, John of Aragon and Castile, was born in Seville on June 30, 1478, which opened new possibilities for dynastic stability of the Isabellian side.. John of Aragon and Castile was born how many years after Isabella and Ferdinand give their first exculpation to the Marquis of Cadiz?