Jamie Jane Blankenhooper is the sister of Amy Duncan and the maternal aunt of PJ, Teddy, Gabe and unknowingly, Charlie and Toby. She first appeared in Sister, Sister, and there we learn that Jamie and Amy do not get along.
Amy and Jamie often fight. In Sister, Sister, the two have talks where Jamie throws butter at Amy, and we learn that Jamie never went to Amy's wedding, and Amy stole Bob Diddlebock from Jamie. They eventually apologize, and Amy gets Diddlebock to go to their house and go out with Jamie.