Answer:
They are two brothers. However much they run, they do not reach each other.
If you drop me I'm sure to crack. But give me a smile and I'll always smile back.
What ship has no captain but two mates?
What has four fingers and a thumb but is not alive?
In the sun it likes to play; In the rain it goes away; Walk or run it always follows; In the mud it always wallows.
How did the farmer find his wife?