Jean-Jacques' father, Jacques Lefranc, was the third of the name to become president of the "Cour des Aides", and he was to be followed by his eldest son and grandson. The family retained the seat at Cayx, and the beautifully sited old chateau was where Jean-Jacques and his brother were reared; as a young man he styled himself Lefranc de Caix. His mother, born Mademoiselle de Caulet, was of the same millieu, her father serving as a "president of the morter" - a judicial rank - at the Parlement de Toulouse, where Jean-Jacques was also to have a brief tenure.