Full grown?

Hey everyone,
i was wondering at what age do cats usually reach "full size"
like when do they STOP growing??
I am just kind of curious..
as my adorable little kitty to the left here..(this is an old picture from abut 2 months ago)
well he just wont stop growing!
Its really quite incredible!!
we have 2 siamese's and the female (i know they are smaller) she is 8 months and i believe 6 pounds... but Otis who is 5 and a half months is HUGE just recently he has been growing like a weed!! He weights just over 13 pounds now and is NOT NOT NOT fat at ALL!!! Its pure HUMONGUSNESS!! hes long and big.. and just .. well big! Crazy. and i heard cats dont stop growing until like 2 years or somthing! He eats a lot yes, but its just crazy. Already at only 6 months he is the biggest cat i have ever owned! Hmm..
anyways.. so just wondering if anyone can tell me when cats reach full development at?
that'd be great! hahah poor guy, hes big but hes SUCH a baby still and NEEDS to be held ALWAYS!! speak of the devil.. here he is.
o and now i need to brag, he seems to be VERY "different" in all aspects..
for instance he comes when called by name ALWAYS everytime no matter what he is doin...
i thought as a joke i would try to teach him tricks and he can sit, beg, roll over and he retrieves on comand..
when we get this crazy little guy we had NO idea what we were in for!! but he is SUCH a joy! heheh he also plays the ball under the cup game with great accuracy! i recomend playing that with your cat! lots of fun!!
ok ok im all done talking..
so anyways..
thanks for yer time!
peace