Kirth was a hedgeknight from the Riverlands, who found himself in the employment of Lord Walter Wyl during the Dornish civil war. He saved the lord's life and was granted a boon; asking to become a knight in House Wyl's service, the lord accepted gladly.
Ser Kirth soon became a knight in the household guard of House Wyl of the Boneway. Over the years in the position, he and the heir to Wyl, Timeon, grew to be close companions. Timeon eventually convinced the Lord to make Kirth his personal guard.
He is currently Lord Timeon Wyl's Guard Captain and still his closest friend.