When Julianne was just 10 and Derek, 13, the siblings left their sheltered home in Utah, along with three older sisters and their divorcing parents, to train as ballroom dance pros at the prestigious London dance school Italia Conti Academy of Theatre Arts.
They moved in with family friends Shirley and Corky Ballas, whose son Mark Ballas also became a "DWTS" pro, and were forced to grow up fast.
Leaving the house every morning at 6:45, they would have to take the subway by themselves to get to school.
"I remember one of my first days there I got off at the wrong train station," Julianne, 25, recalled in the latest issue of People. "I was just standing there thinking, 'Where am I?'"
Julianne especially struggled with being so young in the mature world of ballroom dance. In 2013, she told Cosmopolitan that the adults around her took advantage of her because she was separated from her parents.
"I was 10 years old looking like I was 28, being a very sensual dancer," she told Cosmo. "I was a tormented little kid who had to put on this sexy facade because that was my job and my life. But my heart was the same, and I was this innocent little girl."
Today, the dancer-turned-actress and her brother, 29, attribute their success to the sacrifices they made then.
"People will say, 'How could your parents let you go off to do that?'" Derek, the current "DWTS" champion, told People. "I think it's great that they saw an amazing opportunity. That is the reason we are here today."
The siblings are currently selling out performances on their nationwide Move Live on Tour.