I've put together this list of words that go together for 1 reason or another.
Please add on.
Adult & child
Asleep & awake
Aunt & uncle
Bangers & mash
Bat & ball
Big & little
Black & white
Boy & girl
Bread & butter
Bread & jam
Break & mend
Brother & sister
Cat & mouse
Cats & dogs
Chalk & cheese
Clean & dirty
Cops & robbers
Cowboys & Indians
Cup & saucer
Dance & sing
Dead & alive
Doctor & nurse
Dog & bone
Duke & duchess
East & west
Fast & slow
Fat & thin
Fire & ice
Fire & water
Fish & chips
Float & sink
Food & drink
Freeze & thaw
Fresh & stale
God & goddess
Good & bad
Grandma & granddad
Grow & shrink
Happy & sad
Hard & soft
Here & there
Home & away
Horse & cart
Hot & cold
Husband & wife
In & out
Jelly & ice-cream
King & queen
Knife & fork
Laugh & cry
Letters & numbers
Lock & unlock
Mam & dad
Man & woman
Master & servant
Moon & stars
Near & far
Nephew & niece
New & old
Nice & nasty
Noise & silence
North & south
Old & young
On & off
Open & close
Paint & brush
Paper & pen
Peaches & cream
Pen & ink
Play & work
Prince & princess
Read & write
Rich & poor
Right & left
Right & wrong
Snow & ice
Son & daughter
Spend & save
Sponge & custard
Stamp & shout
Stand & deliver
Stars & stripes
Stop & go
Strawberries & cream
Suck & blow
Sun & moon
Supply & demand
Tall & short
Tea & biscuits
Tea & coffee
Tea & sympathy
Thunder & lightning
Together & apart
Tongue & groove
Toothpaste & toothbrush
Trouble & strife
Under & over
Up & down
Walk & run
Wet & dry
Wine & cheese
Witch & wizard