He also had two sisters, Suzanne-Françoise and Elisabeth-Germaine. César-François was born at the family's Château at Thury which they used as a summer residence.
Siya rin ay may dalawang madre, Suzanne-Françoise at Elisabeth-Germaine. Cesar-François ay ipinanganak at ang pamilya ng kastilyo sa Thury na kanilang ginamit bilang isang tag-araw na paninirahan.