When Nathaniel Peters goes for a walk, he often sings aloud, which may be a genetic trait. His great-grandparents were Maria and Georg von Trapp, who founded the Trapp Family Singers with their children and whose story was the basis for “The Sound of Music.”

Mr. Peters, 30, also appears to have inherited Maria von Trapp’s exuberant climb-every-mountain attitude. “You know that look that a golden lab has when chasing a tennis ball — that’s how Nathaniel chases life,” said Ryan Sayre Patrico, a friend.

Growing up on Martha’s Vineyard, Mr. Peters was bookish and interested in existential questions and distinctive clothing from an early age. “He’s the kind of person who wants to wear bright orange shoelaces in his very fancy dress shoes,” said Clare Rose, a friend. “He’s often seen in a bow tie or some kind of hat.”

Ms. Rose added, “He knows what he likes, and nothing he likes is run of the mill.”

By the fall of 2013, he was a graduate student in theology at Boston College, fluent in Latin, fond of three-piece suits and living in a house on the edge of campus that was full of people studying religion and philosophy.