TWO OF THIS TWO OF THAT

 
Parts of the body seem to come in twos
Why should this be I'm looking for clues
Nobody has more than two eyes to see
We also have two legs to walk I guarantee 

Two ears to hear any kind of lovely sound
Two feet are needed to put on the ground 
I guess it's handy to have for a spare part 
Remember though you only have one heart 

Two nostrils are there for us on our nose 
Nightmare when you have a cold I suppose 
Lungs and kidneys both come in pairs 
More than two we would attract some stares