Roger Bernard IV of Foix-Castelbon

Roger Bernard IV of Foix-Castelbon (c. 1333–1381) inherited the viscounty of Castelbon from his father, Roger Bernard III, and like him held it as vassal of the ruling counts of Foix. He married Géraude de Navailles, who bore him a son, Matthew, and a daughter, Isabella.

Long overshadowed by the senior Foix line, his children inherited the County of Foix itself: Matthew succeeded Count Gaston III Fébus in 1391, and Isabella followed her brother as countess.