Who is Caitlin from The Reckoning and what is their importance?

Caitlin is one of Davydd's illegitimate daughter. Her mother died in childbirth, and she was sent to Llewelyn's court to be raised. She loves her uncle, and her uncle adores her, taking her everywhere he goes. Caitlin despises her father for his repeated attempts to murder her uncle, but she tries to make peace with him before his death.

Caitlin is in love with Hugh, but he is unaware of her feelings. When Elund (his wife)leaves him, she waits for Hugh to mourn the death of his marriage. After she finally tires of waiting and reveals her feelings to Hugh, he responds that a marriage between them is unthinkable since she is a member of the royal house. When Llewelyn dies on the battlefield, Caitlin escapes the war ridden kingdom in search of Hugh. They go onto marry and settle in France.