In 2005, Susan Cowsill met 13-year-old Sean Kelly at a Hootie and the Blowfish concert in Buffalo, New York. As an opening act that night, Cowsill was setting up her merchandise table when Kelly introduced himself.

“This kid came up to me,” she recalled. “He said: ‘My name is Sean Kelly. I’m a big fan of the Cowsills, the dB’s and Hootie and the Blowfish.’ And I’m like: ‘You’re 13 and you’re a fan of a...