By marrying his son Philip the Handsome to the future Queen Joanna of Castile in 1498, Maximilianestablished the Habsburg dynasty in Spain and allowed his grandson Charles to hold the throne of both León-Castile and Aragon, thus making him the first de jure King of Spain. Having outlived hisfather Philip, Charles succeeded Maximilian as Holy Roman Emperor in 1519, and thus ruled both the Holy Roman Empire and the Spanish Empire simultaneously.
Maximilian was born atWiener Neustadt on 22 March 1459. At the time, the Dukes of Burgundy, a cadet branch of the French royal family, with their sophisticated nobility and court culture, were the rulers of vastterritories on the eastern and northern boundaries of modern-day France. The reigning duke of Burgundy, Charles the Bold, was the chief political opponent of Maximilian's father Frederick III.Frederick was concerned about Burgundy's expansive tendencies on the western border of his Holy Roman Empire, and to forestall military conflict, he attempted to secure the marriage of Charles'sonly daughter, Mary of Burgundy, to his son Maximilian. After the Siege of Neuss (1474–75), he was successful. The wedding between Maximilian and Mary took place on the evening of 16 August 1477.