Made king of Westphalia, the short-lived realm created from the states of western Germany (1807-1813), Jerome married the second time to Catharina of Württemberg , with whom he had a another son, Napoléon Joseph Charles Paul Bonaparte, (1822-91) also known as "Prince Napoleon" or "Plon-Plon". Their second child, a daughter, the Princess Mathilde Bonaparte, was prominent during and after the Second French Empire as a hostess. After his own kingdom was dissolved, he was granted the title of Prince of Montfort by the King of Württemberg.
When his nephew, Prince Louis Napoleon, became President of France in 1848, Jerome was made governor of Les Invalides, Paris, the burial place of his famous elder brother Napoleon I of France. He later became Marshal of France, and President of the Senate, in his nephew's regime, and was confirmed in the title of Prince française.