Millette was born in Jacksonville, Florida, and cared for mostly by his mother, Cassandra McNair, and grandmother, Pamela McNair. He said his surroundings were tough ones.
"Not a lot of people had things, and when you don't have things for a long time you pretty much say, 'I'm going to take it from someone else,' he said. "It's block-versus-block, and it turns into a gang thing. Really, everyone is just kind of fending for themselves with not a lot of money."
Seeking a better environment, Millette's grandmother moved him to Fort Wayne and took him to a local rink in search of an activity to help keep him out of trouble. He tried speed skating first but was quickly fascinated by hockey.
"Before hockey, I was getting suspended from school and fighting a lot and doing things I could eventually end up in jail [for] when I got older," he said.
But hockey had its own set of challenges. Millette recalled that he played his first game in speed skates.
"It was kind of goofy," he said with a laugh. "I kind of long-strided it. I didn't touch the puck much."
As he improved as a player, Millette said he had to deal with racist taunts during games. His grandmother prepared him for them.
"She always told me, 'Don't let anyone tell you that you can't play the game,'" he said. "The parents on the other team would kind of yell at me or bang the glass and do gestures at me. It was easy for me because I'd already been through tougher things than that. So for me it was like, 'Wow, this is what you have to do to get me off my game and it's not really working.'"
Millette's life took another significant turn about eight years ago when Rick Scero, who was coaching the Victory Honda Bantam Minor AAA team near Detroit, heard about him from one of his assistants.
That assistant, Dan MacKinnon, who was also the Pittsburgh Penguins' director of player personnel, spotted Millette during an outreach trip to Fort Wayne, Scero said. MacKinnon is now a senior vice president and assistant general manager for the New Jersey Devils.
Scero invited Millette to play for his team in a spring league and marveled that the 12-year-old was "probably one of the hardest practice players I've ever seen. When he practices it's just like a game, every drill."