 Hoping to cement the recent alliance with Austria through a family connection, Napoleon married the Marie Louise, Duchess of Parma, daughter of Francis II, who was 18 years old at the time.On 20 March 1811, Marie Louise gave birth to a baby boy, whom Napoleon made heir apparent and bestowed the title of "King of Rome".His son never actually ruled the empire, but given his brief titular rule and cousin Louis-Napoléon's subsequent naming himself Napoléon III, historians often refer to him as "Napoleon II".