Derek and Julianna Hough, <EM>Dancing with the Stars</EM> Derek and Julianna Hough, Dancing with the Stars

A petite blonde woman sits spellbound in the Dancing with the Stars (Mondays, 8 pm/ET and Tuesdays 9 pm/ET, ABC) studio audience as the couples make their entrances. Last season, Marriann Nelson screamed herself hoarse cheering for her daughter, the sensational young ballroom pro Julianne Hough. "This season," she says, "I thought, 'I'll be calm.' But when they both came out — my daughter on one side and my son on the other — I just lost it."

Mom isn't the only one wild about Julianne, 19, and her equally talented big brother, Derek, 22. Julianne danced her way into the winner's circle last season with Olympic speed skater Apolo Anton Ohno and poses a serious threat once again with her new partner, two-time Indy 500 winner Helio Castroneves. And newcomer Derek has shown remarkable grace under pressure by regaining his footing with Beverly Hills, 90210 star Jennie Garth after the two slipped and fell at the end of the second week's performance. "It's good when things like that happen sometimes," he says, "just to remind people that this is real, this is live."

If these two show unusual maturity for such young performers, it's because they've been rehearsing all their lives. "At one time, I thought we would be the blonde Osmonds," says Nelson, who raised her five children in Salt Lake City with her first husband, Bruce Hough. Marriann enrolled her brood in a variety of performing-arts classes beginning at age 3. "I always wanted my kids to be independent and self-sufficient," Nelson says. "Not afraid of the world."

The first tough life lesson came when Julianne was 9 and her parents divorced. Marriann, looking for "one-stop shopping" for her children's varied classes, enrolled them in West Orem's Center Stage Performing Arts Studio. Derek was inspired by British dance teachers who came to visit and asked to study with them in London. Julianne, only 10, followed him abroad six months later. They lived with their teachers, Corky and Shirley Ballas, world champion ballroom dancers and the parents of Mark Ballas, the other new Dancing pro this season. "Mark's parents are still really powerful in the competition world," Derek says. "We'd go to competitions — Julianne with Mark and me with my partner — and everyone would go, 'Oh, man. The brat pack has arrived.'"

Julianne, Derek and Mark all became youth world champions. "I wasn't homesick until I was 15," says Julianne, who returned to the U.S. that year. "I felt that I was really just focusing on dance, and I wanted to experience high school — which I ended up hating, by the way."

But she graduated (as did Derek) and decided to move to Los Angeles in hopes of launching a singing and dancing career. Dancing pro Louis van Amstel put her name forward as a company dancer for the DWTS winter tour in 2006. And when Julianne heard that tour producers were searching for more male dancers, she said, "My brother's home for six weeks on vacation. You want him?" The rest is Dancing history.

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