spot the difference

one of us sleeps through the night (and day)
the other one wakes up intermittently to snack and party
one of us need never wear no nappy
the other one emits explosive poops and pops
one of us never dribbles, ever
the other one salivates because he can't swallow his own drool yet
one of us does not need hair combed or nails clipped
the other one has fearsome hair on his back and nails that can scratch eyes out
one of us closes our eyes when the dummy gets popped in
the other one closes his eyes only when exhausted or in deep slumber
one of us can only visualise our hands from a distance
the other one sucks at his fingers and thumb at every opportunity
one of us never ever makes a noise or cries
the other one can launch into (incomprehensible) loud 'conversations' at 4am
replete with coos, shrieks, snuffles, squeaks, squeals and squawks
one of us only ever has one expression on his face
the other one has a myriad of smiles, gurgles, frowns, grins, cringes, wails, laughs,
and ably expresses astonishment and delight, joy and sadness,
frustration and contentment, surprise and amusement
one of us will always wear the same-sized clothes
the other one keeps growing like there is no tomorrow
one of us stays still in one position when manipulated
the other one can sit still for a few seconds, kicks and flaps about
and occasionally overbalances and keels over
one of us hardly ever needs a bath
the other one rather likes splashing about in the water
one of us is quite hard and unwieldy
the other one is soft yet firm, tender and smooshy,
squeezable and smooth as, cuddly and oh so warm,
eminently and incontrovertibly munchable
one of us is played with occasionally then left around
the other one is held so dear, cherished to bits
and loved so deeply like nothing else in the world...
one of us has an elder brother with a wicked sense of humour -
"mum... callum looks like a zebra today!"
can you guess which one i am?