In 1469, the two largest northern and central Spanish states, Castile and Aragon, were ruled by the marriage of Ferdinand and Isabella. The union was formed when the marriage between Ferdinand and Isabel took place on October 19, 1469, of Ferdinand, heir to the throne of the kingdom Aragon, with Isabella, heiress to the kingdom of Castile. A disputed succession was to cost Isabella a decade of fighting before her position was made safe. Since the bride and groom were relatives,( they were royal cousins) the Pope gave dispensation in order to get married. This document was duly produced, but it was actually a forgery, created by Ferdinand himself; his father, the king of Aragon; and the archbishop of Toledo. Castile and Aragon remained distinct, and the union was at first a personal one only; one would hardly imagine it would survive Ferdinand and Isabella. The power of the crown extended their reign through conquering other independent regions in Spain in the so-called Reconquista forcing back the Muslim across the Straits of Gibraltar.
The crown was inherited by the grandson of Ferdinand and Isabella, Holy Roman Emperor Charles V, who became Charles I of Spain. His rule began in the early 1600's , this was the beggining of a period of Habsburg rule in Spain that united the Spanish crown with the lands in the Holy Roman Empire.
