Julianne Hough Performs “I Just Had Sex” on Lip Sync Battle, Mortifies Brother Derek Hough: Watch!

Horrified Hough!

Julianne Hough got down and dirty on Lip Sync Battle's dance floor — and her brother Derek Hough had a front row seat! The Dancing With the Stars siblings competed against each other on an upcoming episode of the Spike TV series, with Julianne leaving little to the imagination during her performance of Lonely Island's "I Just Had Sex".

"Have you ever had sex? I did, it felt great!" the DWTS judge, 26, belts out. "It feels so good when I did it with my penis."

Julianne shakes her booty, whips her hair back and forth (a la Willow Smith), and grinds to the overtly sexual tune.

derek and julianne
Julianne and Derek Hough on Lip Sync Battle

As for Derek? Well, Julianne gave a memorable show, but it was her older brother, 29, that kept the audience laughing with his hilarious reactions.

Seriously, that face!

Watch the video above!

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