What happened to the dad of the kid from up?

In the movie "Up," it's implied that Carl Fredricksen's wife, Ellie, passed away, leaving him heartbroken. The film does not explicitly mention the father of the young boy, Russell, but it suggests that Russell's parents are often busy and neglectful, leading him to seek approval and companionship from Carl. The focus is primarily on Carl's journey and relationship with Russell rather than delving deeply into Russell's family dynamics.