Jean-Baptiste Marie de Piquet was born on 5 August 1729 in Arles, France, during the time of the Great Plague of Marseille. The heroism of his father, Guillaume de Piquet (1689-1747), the Marquess of Méjanes, resulted in the land of Méjanes being raised to marquisate status in 1723. Piquet inherited this land in 1748 following his father's death.