Sibling Rivalry: A Brother and Sister Compete to Win on 'Dancing with the Stars'

She is now remarried but still supportive of her children.

"I cried … but I think that's where the kids really developed a lot of strength. Toughness, really," she said.

With their English dance coaches also acting as surrogate parents, Derek and Julianne won a series of world championships, setting the stage for Julianne's victory in her first year as a dancer on season four's "Dancing With the Stars." The winning chemistry between Julianne and then-dance partner, Olympic speed skater Apolo Anton Ohno, was so great, some speculated that it existed off the dance floor as well. That's all rumors and speculation, according to Julianne and her mother.

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"I asked her, 'You sure you don't like him, 'cause we all do,'" Marianne said. "She says, 'Mom, it's like dancing with my brother.'"

Trials and Tribulations

When the season began this year, Julianne was back with a new partner -- Indy 500 champion Helio Castroneves. Derek joined the show for the first time, teamed with former Beverly Hills 90210 star Jennie Garth, who had some serious doubts about Derek as a leading man.

"I remember my little girls were peering out the windows, watching him walk up the walkway," recalled Garth. "And they came running down, and they were like, he's so young, he looks really little!" she laughed.

But any reservations she may have had based on his appearance were quickly lost when Derek showed amazing calm under pressure, helping Jennie overcome an awkward fall during their second dance together.

"I think it was quick step, and it went really well, and we were sort of flying by the seat of our pants," she recalled. "We had this great move planned for the end, and it was very exciting. Very like brave of us, and we did it, but we didn't account for the dress, and the dress just sort of slipped right under his shoe."

And so went "The Fall" as show fans have dubbed it. Both dancers ended on the ground, but Derek was the first to spring up and offer a mortified Garth his hand and reassuring words.

"I said, 'You know what? Do not worry about this; I've already got a plan. I know next week you're going to come back, we're going to tango, and you're going to do amazing,'" Derek said. "And she did."