The death of Charles III, Duke of Burgundy in 1611 meant that the heir to the Dukedom of Burgundy and all its associated titles were left on the shoulders of the infant Maximilian I, Duke of Burgundy, only son of the Duke’s son Philip of Burgundy, and his wife Constance of Austria. Thus, the new heir was the new Duke’s eldest sister, Christina of Burgundy, currently the wife of Philip IV of Castile, but formerly, having produced a son, the wife of Cosimo II de Medici, Grand Duke of Tuscany. Thus, the next Duke of Burgundy might have be young Ferdinando II de Medici, Grand Duke of Tuscany.
In Castile, the royal family found themselves split. On one side stood the King, his wife, and their young daughter, Marianna of Castile, the newborn Infanta and current Princess of Asturias. On the other side stood the Infante Diego, the younger brother of Philip IV of Castile, and his two sons by Isabella of Viseu, the Infantes Maximilian and Philip of Castile. Now, the reason for this divide was complicated, but in simple terms, the brothers were the result of two different marriages for their father, the King to Elisabeth of Austria and the Infante Diego to the Princess Christina of Bavaria, currently the Queen Dowager. The two had almost 15 years between them, and were actually their father’s only surviving children, but by 1611, when the two were odds, mostly due to the issues surrounding the Infanta Marianna’s birth. For, with her birth, Diego went from the heir to Castile and Portugal to just it’s Infante.
Now, this feud had been ongoing since the death of Philip III of Castile, in 1603. His health had never been good, and by the time he had died, he had seen his eldest son’s first marriage, to the Lady Margherita Gonzaga, fall apart in a series of mistresses, betrayals and miscarriages. Thus, when the two rose to the throne, it seemed that Diego, or at least his line, would inherit the throne, and he was married to the Portuguese/Aragonese Princess Isabella of Viseu. However, when Margherita Gonzaga followed her father-in-law to the grave in 1609, Philip IV of Castile had seen his chance to keep his line on the throne, and had shortly after married the recently widowed Grand Duchess of Tuscany, in 1610.
Now, the royal family was at odds, and in early 1612, it came to an odd head, with Philip IV on one side, backed by the Duke of Burgundy, and Diego on the other, citing his brother’s lack of competence, on the other side, backed by the King of Aragon. Now this was important, because, as part of their alliance, “King Diego I of Castile” promised to cede Portugal to Juan of Viseu, a cousin to the King of Aragon and Afonso of Aragon’s eldest son, currently married to Beatrice d’Aragona, a niece of his grandfather’s mistress, Maria d’Aragona.