During the French Revolution, Joseph was often absent on foreign travels in order to secure loans for his father.

During the Terror of Robespierre, these foreign trips placed him under suspicion for counterrevolutionary activity.

This caused him to be declared a traitor in his absence, and resulted in the arrest of his wife, father, brother and sister-in-law in Paris.

When his brother became Prince of Monaco in 1814, but was unable to manage the affairs of state because of poor health, Joseph was appointed regent.

They had issue: Prince Joseph remarried to Frances Doyle, widow of Major-General Wellbore Ellis Doyle (d.1798) and daughter of Edward Rainsford of Richmond, Co. Dublin.