A woman has 7 children, and exactly half of them are boys. How 
is this possible? 

All her children are boys.

A cloud was my mother, the wind is my father, my son is the cool 
stream, and my daughter is the fruit of the land. A rainbow is 
my bed, the earth my final resting place, and I'm the torment of man. 

Rain

Who is he that runneth through the hedge, his house on his back?

A snail.

What is it that has four legs, one head and a foot?

A bed.

When can you add two to eleven and get one as the correct 
answer? 

When you add two hours to eleven o'clock, you get one o'clock.

I know a word of letters three.
Add two, and fewer there will be?

Fewer.