Three brothers share a family sport:
A non-stop marathon
The oldest one is fat and short
And trudges slowly on
The middle brother's tall and slim
And keeps a steady pace
The youngest runs just like the wind,
A-speeding through the race

"He's young in years, we let him run,"
The other brothers say
"'cause though he's surely number one,
He's second, in a way."


What are we?