Joyeuse Frey

Joyeuse Erenford is a minor character in Game of Thrones, making her debut in the ninth episode of the first season.

Joyeuse Erenford is 15 years old and the eighth wife of Lord Walder Frey.

Cripples, Bastards and Broken Things
Catelyn Stark talks to a knight of House Frey at the Crossroads Inn. He tells her that Lord Walder is about to celebrate his 90th nameday and has taken another wife in celebration of the event. Tyrion Lannister finds this notion amusing, at least until the Frey knight agrees to help Catelyn take Tyrion prisoner for the attempted murder of her son Bran.

Baelor
Arriving that the Twins, Catelyn grees Lord Walder Frey and his young, 15-year-old wife, Lady Joyeuse. Walder dismisses his family, including Joyeuse, whilst he and Catelyn haggle on what price the Starks will pay to be allowed to cross the river.

In the books
In the books, Lady Joyeuse is slightly older than in the TV show, aged sixteen. House Erenford is a minor vassal house of the Riverlands, sworn to House Frey.