Just what the title says. What if Juan Prince de Asturias, son of Queen Isabella I of Castile and King Ferdinand II of Aragon, survives and succeeds to the throne? The first obvious change is the Habsburgs don't inherit Spain, Italy and the American Colonies but what then? Would Spain ally itself with France, or keep its alliance with the Habsburgs? Who would the future Charles V marry? Is there a chance that The Habsburgs would stay neutral in Francis I's wars in Italy?