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

Caitlin is one of six illegitimate daughters of Davydd. Her mother dies in childbirth, so she is sent to Llewelyn's court to be raised. She loves her uncle, and Llewelyn adores her. He takes her everywhere he goes. She despises her father for his attempts to murder her uncle, but seeks to make peace with him before he dies. Caitlin loves Hugh, and waits for him when he is married to Elund. When Elund leaves Hugh, she again waits for Hugh to mourn the death of his marriage. She finally tires of waiting and reveals her feelings to Hugh, but a marriage is unthinkable since she is a member of the royal house and he is a landless knight. When Llewelyn dies on the battlefield, Wales no longer holds Caitlin and she escapes the war ridden kingdom in search of Hugh. They marry and settle in France.