Bill Gates vs. Elon Musk

When Gates was a kid, he spent so much time reading that his parents finally forbade him from bringing books to the dinner table. Gates took a break from classes his senior year in high school to do programming with his friend Paul Allen at a power plant in North Bonneville, Washington.

Musk, who says he's worried about population collapse, has nine children with three women, including triplets and two sets of twins. As a kid in South Africa, Musk taught himself to code; he sold his first game, Blastar, for about $500.