Joy Osmanski as Jing (seasons 2–3; recurring, season 1), Duncan and Kimberly's adopted five-year-old Asian little sister who has an open crush on Duncan, though she loses romantic interest in the second season.

Along with Duncan lives his mom, Annie, a parking enforcement officer who dreams of being a detective, his dad, Jack, who tries to be a better father figure to Duncan than his father was to him; his sister Kimberly, who is a normal teenager going through normal teen-phases; and his adopted sister Jing, an intelligent 5-year-old always giving Duncan advice.