Vaillant’s other main interest is the power of relationships. “It is social aptitude,” he writes, “not intellectual brilliance or parental social class, that leads to successful aging.” Warm connections are necessary—and if not found in a mother or father, they can come from siblings, uncles, friends, mentors. The men’s relationships at age 47, he found, predicted late-life adjustment better than any other variable, except defenses. Good sibling relationships seem especially powerful: 93 percent of the men who were thriving at age 65 had been close to a brother or sister when younger. In an interview in the March 2008 newsletter to the Grant Study subjects, Vaillant was asked, “What have you learned from the Grant Study men?” Vaillant’s response: “That the only thing that really matters in life are your relationships to other people.”