Lord Westfall is the father of Chaol and Terrin, and the lord of Anielle, who swore loyalty to Adarlan and House Havilliard.
The lord of Anielle never makes a physical appearance throughout the books, but is indirectly mentioned in Throne of Glass. He had spent most of his life defending the villagers from the cruel, mountain tribes of White Fang Mountains. This has changed after the conquest of the local freefolk, bringing peace to the people of Anielle, and lord Westfall could finally focus on developing their wellfare.
His son, Chaol, had left the title of his heir, in order to become the captain of Rifthold's palace guard and stay near to his best friend, prince Dorian. In the process, Chaol's younger brother, Terrin had become an heir to the throne.