His mother, Suzanne-Françoise Charpentier, married Jacques Cassini in 1710 and they had five children. César-François had two brothers; Dominique-Jean was the eldest and followed his father into the Chambre des Comptes, while Dominique-Joseph, César-François's younger brother, went on to a military career.
Kanyang ina, Suzanne-Françoise Charpentier, may asawa Jacques Cassini sa 1710 at sila ay may limang mga anak. Cesar-François may dalawang kapatid na lalaki; Dominique-Jean ay ang pinakamatanda at sinundan ng kanyang ama sa Chambre des ng Comptes, habang Dominique-Joseph, ANTONIO-François ng batang kapatid na lalaki, nagpunta sa militar sa isang karera.