He is definately growing, that's for sure....
I'd like to see him put some weight on tho. He's quite slim but that could just be my preference... I like kitties, even hoomans, with a little flesh on them. It could be that he's approaching 6mos, his long fur is silky and lays flat, as opposed to Kizzy who at 6mos was bigger, fluffier, etc.... so I think Kitchi is tiny, when really he isn't. Or it could be that Kitchi prefers wet food, so he's not gaining "extra" weight.
He's bout 6lbs I would say.... he hasn't been weighed in a couple months.
I'm sure he'll gain some weight when he's neutered.