The French also used courtesy titles, but in a different way. Just as in the United Kingdom, each title in France was held by one person only; as a matter of fact, each title was specficially attached to a piece of land. Although all legitimate children of a nobleman were also noble, they had no right to use his titles, unless he actually gave them legal ownership of the piece of land it was attached to. Nevertheless, for purposes of presentation at Court, a noble person would obtain permission from the head of the family and from the king to use one of the family's lesser titles. Unlike in the United Kingdom system, courtesy titles were not limited to the eldest son, but were used by all the children. Furthermore, they could be of the same rank as the head of the family's main title.
For example, in the 17th century the duke of Mortemart was also duke of Vivonne and prince of Tonnay-Charente. The eldest son was known as the duke of Vivonne, and one of the daughters was known was Mlle de Tonnay-Charente. If, as was sometimes the case, the family didn't have suitable lesser titles for a male family member, he might be known as the chevalier de X.
There were no hard and fast rules in this, and each family had its own traditions concerning what titles were used by whom. This wasn't always held to, though, and sometimes even the head of the family would decide to be known by a different title. This most illustrious example of this was the 7th prince of Condé, who was always known as the duke of Bourbon, a title that had been used by the grandsons of the Bourbon-Condé family during the 17th century.