Can a cat weigh 17 lb 8 oz (8 kilograms) and be healthy?

Certain breeds can grow up to 25lbs and still be healthy and not overweight, if he's active and can clean himself and doesn't look like he has a pot belly then he's just big boned and perhaps has heavy muscles, perhaps help him lose a little weight by playing with him more and forcing him to be running around, if your other two are normal weight then he's obviously not being overfed, again so long as he can run around and clean himself all over then he's not overweight