First English Edition. Jérôme-Napoléon Bonaparte (born Girolamo Buonaparte; 15 November 1784 – 24 June 1860) was the youngest brother of Napoleon I and reigned as Jerome Napoleon I (formally Hieronymus Napoleon in German), King of Westphalia, between 1807 and 1813. Historian Owen Connelly points to his financial, military, and administrative successes and concludes he was a loyal, useful, and soldierly asset to Napoleon. From 1816 onward, he bore the title of Prince of Montfort. After 1848, when his nephew, Louis Napoleon, became President of the French Second Republic, he served in several official roles, including Marshal of France from 1850 onward, and President of the Senate in 1852.