Frail, weak, shy and sensitive as a youth, Bobby Kennedy was a prime candidate for sissyhood, but he decided to remake himself. Even though he was smallish, and not a great athlete, he fought his way onto the Harvard football team, and through injuries, e.g. dislocated shoulder, fractured leg. His coaches were so impressed, he was awarded a varsity letter, something neither Joe nor Jack had achieved.
That tenacity would serve him well as Jack Kennedy's campaign manager, and then as attorney general.
From Brothers, by Geo. Howe Colt