Gerald Johanssen, Arnold's best friend. He and his family are African-Americans. Throughout the series both he and Phoebe, another classmate, have a love interest in one another.
Martin Johanssen, his father. a Businessman, he is obsessed with saving money, often going over the top on the price of things like the Electric Bill. It is revealed he is a Vietnam Veteran, and earned Gerald's respect when Gerald finds out his father, a messenger and staff officer, saved the life of a downed Helicopter pilot.
Mrs. Johanssen (first name unknown), his mother, works in the Corner Store as a cashier as seen in the Season 1 episode, "Helga's Makeover".
Jamie O. Johanssen, his older brother, who often bullies him and takes his stuff.
Timberly Johanssen, his younger sister, who's innocent actions often cause him trouble.