Philip I of Castile

Philip inherited the Burgundian Netherlands at three when his mother Mary died in 1482, becoming the first Habsburg to hold those rich domains. Though France contested parts of the inheritance, treaties in 1482 and 1493 largely secured it, and he proved an effective ruler who favored peace and trade. In 1496 his father Maximilian arranged his marriage to Joanna, second daughter of Isabella and Ferdinand of Spain - a parallel swap that saw Philip's sister Margaret marry Joanna's brother. After the deaths of her siblings and nephew, Joanna became heir to Castile and Aragon. Philip spent his time in Spain consolidating power, clashing with his wife and father-in-law. When Isabella died in 1504 Joanna became queen; Philip was proclaimed king in 1506 but died that September, leaving Joanna shattered. Ferdinand and their son Charles moved quickly to confine her for alleged insanity, and Charles eventually united the Habsburg, Burgundian, and Spanish crowns - an empire Philip's marriage had made possible.