Is he still young and very active? He might burn up those calories in the food faster than his overweight brother. For example, I have a teenaged son at home who will eat us out of house and home. He easily eats 4000 calories a day. Yet he is stick thin and barely hit 140 on the scales at nearly 6' tall! I would think the same rule applies to cats too - the active ones are able to eat more because they are using more of the "fuel" than the inactive ones. Pouncer's always running up to me as if he's starving to death. I'll usually feed him because I see how active he is. He's a year old, so still a lot of kitten in him. Now his BIG brother? Allen gets fed only once a day, but he doesn't beg for it after he's fed either.