Portrait of Isabella of Portugal, wife of Holy Roman Emperor Charles V by  Titian, 1548Sou

Portrait of Isabella of Portugal, wife of Holy Roman Emperor Charles V by Titian, 1548

Source

Isabella married her first cousin, Charles V, who as Holy Roman Emperor, King of Spain, Archduke of the Habsburg dominions, titular Duke of Burgundy, and ruler of the Netherlands and the Spanish empire in the Americas and the Mediterranean and Italy was one of the most powerful men of his time. 

Although it was a political union, the marriage proved to be a love-match. Records say that during their honeymoon “when they are together, although there are many people around, they do not notice anyone else; they talk and laugh, and nothing else distracts them.”