 What makes Johnson's son so different?
He came near starving and moved on to Titan. It's bitter as some kinds of sin before it's purified. What's fair is fair, and you have put a different complexion on what seemed at first to be an unconscionable interjection of a middleman between Nature and man's thirst." "On account of the quantity, I'm able to quote a bargain price. The planetoid man worked the pump while the mayor intently watched the crude level-gauge, crying "Stop!" when it registered the proper amount. Then Johnson rubbed his thumb on his index finger and wetted his lips expectantly. "Johnson, as I saw instantly, is the victim of a difficult environment, and must charge accordingly."
 He grew up without Earth's gravity, allowing him to grow larger than most people.
 He grew up without Earth's gravity, allowing him to grow larger than most people.  He is much larger than the average man.  Like Genius, he is not human.  He's been living isolated from other humans with his father.