The actor left the cast of Grounded For Life when his family moved away. Was not replaced. His last appearance was Episode 78 - "Space Camp Oddity." I don't think it was ever explained - the character just vanished.
At the beginning of season five of Grounded For Life, Jake Burbage, the actor that played Henry Finnerty, left the show to move back to New Jersey with his family. He is not seen on the show again,...
he youngest son of the family, Henry, disappeared at the beginning of the fifth season when actor Burbage left to move back east with his family. He is actually never seen during the fifth season but...