Spain

There were 2 kingdoms in Spain, Castile and Aragon. (Actually, there were several, but the others don't count.)

Castile was ruled by Queen Isabella (1474-1504), who married Ferdinand V, King of Aragon (1479-1516). They united the Spanish crown, and further strengthened it by kicking the moors out of the old Kingdom of Granada. They had various children, the most important, from our point-of-view, were Katharine of Aragon, who married Henry VIII and Joanna (Juana) the Mad. She married Philip of Burgundy.

When Isabella died (1504), Philip and Joanna became joint rulers of Castile, until Philip's death in 1506. Because Joanna was not only a woman but, moreover, mad, Ferdinand became regent of Castile, although Juana remained nominal queen of Castile until 1555 (and became nominal queen of Aragon in 1516). When Ferdinand died (1516), his grandson, Joanna and Philip's son, Charles I (or Charles V, in HRE terms) became king.

Here's a film

about Joanna;

looks interesting

(and racey!)