The Catholic Monarchs (Spanish: Reyes Católicos) is the joint title used in history for Queen Isabella I of Castile and King Ferdinand II of Aragon. They were both from the House of Trastámara and were second cousins, being both descended from John I of Castile; on marriage they were given a papal dispensation to deal with consanguinity by Sixtus IV. They married on October 19, 1469, in the city of Valladolid; Isabella was eighteen years old and Ferdinand a year younger; this marriage united both kingdoms under one crown. It is generally accepted by most scholars (John Elliott being an English-speaking example) that the unification of Spain can essentially be traced back to the marriage of Ferdinand and Isabella. Some newer historical opinions propose that under their rule, what later beca