big?

So on more than 972 occasions I have heard "boy, he sure is big for his age" or "He's going to be a BIG man"
Here's my question... is he really THAT big? He seems, to me, that he's just the right size, just perfect...
But really, mom's out there - do you think that he is BIG for his age? I haven't been around TONS of kids his ago nor would I remember even if I had. I also do not remember Jett at that age - thus I know not what I speak of...
KNOCK ON WOOD we have not been to the doctor since his 18 month check up so... I do not know his "status" (( and i don't think they even told me then...?))

Thanks for the input...