Maria Kilbourne is the 8-year-old sister of Shannon and Tiffany Kilbourne. She attends Stoneybrook Day School with her older sisters.
Maria is described as having dark, reddish-brown hair & hazel-brown eyes. She likes homework, math, and word searches. While it looked like she was going to be a bookworm, Maria became more outgoing and athletic. She is a member of the Stoneybrook Day School swim team where has won trophies for swimming butterfly stroke and holds the school record for breast stroke.
Maria's bedroom is described as having pink wallpaper with a heart pattern, stuffed animals propped up all over, and framed swim team photos over her desk.