If you haven't read "Harris and Me: A Summer Remembered" you really should. It is a great story about the narrator, a boy a bit older than Harris is sent to live with the Larson's for the summer because of his irresponsible parents. Harris and the narrator are cousins and they manage get into all types of trouble. Harris is constantly coming up with schemes for them to try and something always goes wrong.
One of the sidecharacters who really stuck in my mind was Harris's fourteen-year-old sister, Glennis. While Mr. and Mrs Larson are busy being adults and running the farm and the household Glennis is a mother figure to Harris. She is constantly slapping Harris in the head for using the wrong type of language. Most of the characters are back stories to Harris's schemes.