In 1962, the Osmond brothers Alan, Wayne, Merrill and Jay were discovered by Williams' father and signed on as regulars on NBC's "The Andy Williams Show." Half a century later, Alan Osmond remains grateful.
"He had the best TV show, I believe," he said. "We grew up on 'The Andy Williams Show.' And he threw everything behind us, even though we were just no-names out of Ogden, Utah.
"He and his brothers performed as a quartet when they were young, and I think that resonated with him and his family. And Don, his brother, was our manager. So our families were, like, related."
Donny Osmond, who made his national TV debut on Williams' show in 1963, called the singer "an inspiring man in both his life and his music," adding that he "will ever be indebted to Andy for giving me the opportunity to fulfill my dreams and the opportunity to be personally inspired by such a generous talent."
Both brothers raved about Williams' voice.
"He truly was a great singer," Donny Osmond said. "I will always treasure the memories of when I was 7 years old and he took the time to give me several voice lessons."
"He was probably the best singer in the world and, at this point, the best singer out of this world," Alan Osmond said. "He was a great, great guy. He was like a big brother, almost."
Not only did Williams launch the careers of the original Osmond brothers, but Donny, Marie and Jimmy made their first national TV appearances on the show as well.
"I am so sad Andy Williams passed away," Jimmy Osmond said on Twitter. "It just doesn't seem possible. He was my mentor and I will forever be grateful for his friendship."
Williams also helped launch Alan Osmond's sons, the Osmond Boys (aka the Osmonds-Second Generation). And he remained close to the family.
"We've been in discussions with our granddaughters, who are known as the Osmond Girls, and Andy was going to launch them," Alan Osmond said. "So you've got to know how close we are to him. He really was like a member of our family."