"Our home videos are pretty self-evident that these kids loved to shake, rattle and roll," their dad, Bruce Hough, tells PEOPLE.
Now the siblings, who gained fame on ABC's Dancing with the Stars, are doing just that on their summer Move Live on Tour, selling out venues across the country.
But as Julianne, 25, and Derek, 29, recount in PEOPLE’s new cover story, the success they've found on the dance floor came at a hefty price.
When Julianne was just 10 and Derek was 13, they left their sheltered life in Utah, as well as their three older sisters and parents (who were then going through a divorce), for the prestigious London dance school Italia Conti Academy of Theatre Arts to train as ballroom dance pros.
Moving in with family friends Shirley and Corky Ballas (whose son Mark also became a DWTS pro), they endured a grueling schedule that had them leaving the house every morning at 6:45, taking the subway by themselves and heading to school. "I remember one of my first days there I got off at the wrong train station," Julianne says. "I was just standing there thinking, 'Where am I?' "
They battled homesickness, and young Julianne especially struggled with the pressure of trying to fit into the mature world of ballroom dance. Thanks to her spray tans and competition makeup, "When I look back, I think it’s so sad I have no pictures of me with a cute, bare, 10-year-old face," she says.
But today, the two agree that their success is due to the sacrifices they made as kids and their years of hard work.
"People will say, 'How could your parents let you go off to do that?' " Derek says. "I think it's great that they saw an amazing opportunity. That is the reason we are here today."
For more on the Houghs' childhood and their close bond today, plus personal photos of them growing up, pick up the latest issue of PEOPLE, on newsstands Friday