[2] He was his father's first son but due to his illegitimacy, was not allowed to inherit the throne; his half-brother, the future Louis XIII of France was born in September 1601 much to the joy of the king.

[4] César was involved in many noble intrigues during the reign of his half-brother Louis XIII of France.

Soon after his return he took part in the cabale des Importants against Cardinal Mazarin, together with his second son François - this led to yet another exile, till 1650.

The marriage of his son Louis to Laura Mancini brought about his reconciliation with Mazarin, and he supported Anne of Austria throughout the Fronde.

Joining French forces in the ongoing war with Spain, he defeated a Spanish fleet off Barcelona in 1655.