He served briefly as a personal assistant of the revolutionary leader Pasquale Paoli and eventually rose to become Corsica's representative to the court of Louis XVI. It was well after his death that his second surviving son, Napoleon, became Emperor of the French; subsequently, several of Buonaparte's other children received royal titles from their brother, and married into royalty.
Carlo Buonaparte was born in Ajaccio, Corsica as the youngest of three children. His father, Nobile Giuseppe Buonaparte, had represented Ajaccio at the Council of Corte in 1749. The Corsican Buonapartes were descended from minor Italian nobility of Tuscan origin, who had come to Corsica from Liguria in the 16th century.
Carlo initially followed in his father's footsteps and studied to be a lawyer at Pisa University, but following a substantial inheritance from the death of his father, he left before earning his degree to tend to his inheritance and take charge of family responsibilities. Shortly afterwards, he married Donna Maria Letizia Ramolino. Both were of Corsican nobility, and very young at the time of their marriage (Carlo was seventeen and Letizia was thirteen), but this was typical of their society at that time. Their marriage was arranged by their families, also typical of their milieu; economic convenience was only one of several factors considered while arranging the match, the main considerations being of cultural compatibility in matters such as speech dialict, church habits, food habits, attire and other family traditions. Buonaparte's new wife brought with her a dowry of thirty-one acres of land, including a mill and bakery which yielded an annual income of roughly £10,000.
For a period after his marriage at Ajaccio on 2/7 June 1764, he worked as a secretary and personal assistant to Pasquale Paoli. He had a son, Napoleone, who died in infancy in 1765 as did a daughter. Paoli sent him to Rome to negotiate with Pope Clement XIII in 1766. He had apparently enjoyed his time in Rome up until being forced for reasons unknown back to Corsica in 1768 - though he had possibly enjoyed an affair with a married woman during his stay which led to his departure. At the time of his return, the Republic of Genoa had offered Corsica to Louis XV as payment for a debt. The French were eager to obtain the strategically placed island for the protection of their own coasts, and Genoa equally keen to relinquish control given their inability to resist growing independence movements. Buonaparte was noted for a fervent speech against the French "invasion". Political upheaval followed as France gained ownership of Corsica, and many of Paoli's supporters had to flee to the mountains. Buonaparte and his family, now boasting newborn Giuseppe, who was the first child to survive infancy, were included. The family eventually returned to the town, where Buonaparte's wife gave birth to third son, another Napoleone, within Ajaccio Cathedral.
Soon after French acquisition of the island, Carlo Buonaparte embraced the new government. He was appointed Assessor of the Royal Jurisdiction of Ajaccio and the neighbouring districts on 20 September 1769. Shortly after that he became a Doctor in Laws at the University of Pisa on 27 November 1769.