B.J. and Justin Upton. Dom and Joe DiMaggio. Billy Ripken and Cal Ripken, Jr. Every era of baseball offers brother combos to study, and when Frank Sulloway and Richard Zweigenhaft set out to study if the behavioral differences between younger and older siblings showed up on the diamond, the answer was a resounding 'yes.'

In 90 percent of the siblings studied, the little brother attempted more stolen bases than the older brother, seemingly living up to the "risk-taker" tendency of younger siblings.