Can you imagine watching your little sister bumping, grinding, writhing, and literally crawling on all fours alongside two hot shirtless guys while lip syncing to "I Just Had Sex"? Derek Hough did not have to imagine. The "Dancing With the Stars" pro watched his sister Julianne Hough, a "Dancing With the Stars" judge, do just that on the May 14 episode of "Lip Sync Battle." It was glorious. She won, obviously, and she left her brother scarred for life, which is a bonus.

There were two rounds of battle, as usual, and Julianne owned both. She had backup from Meghan Trainor herself for "All About That Bass," which competed against Derek's "Can't Hold Us" by Macklemore & Ryan Lewis. The second round could've been tough, since Derek upped his game with a wild Sia wig for an appropriately bizarre rendition of "Chandelier." But it was all over once Jules hit the floor for The Lonely Island's "Sex" song. When she won, Julianne said she'd put her new trophy up on the fireplace mantel to show it off.

Derek commented on his sister's win in his TV Guide blog (which he's keeping through DWTS Season 20):

Speaking of kicking butt, Julianne destroyed me on Lip Sync Battle! Our episode airs Thursday... and I can't even. She sang the most inappropriate song. No brother should have to sit and watch that! It was so inappropriate and it was just so bad! She did great, but oh, my God! But here's the thing: As much as I hated it, I had a lot of respect for her. I would never have the balls to do something like that -- just something so inappropriate and be so confident about it. What I love about it is that she was like, 'Hey, this is my sense of humor. I find this song funny and this show is not serious, so I'm gonna go and do it.' As soon as she started singing, I was like, 'I'm leaving!' She played dirty!"

It's true. Julianne is the more bold of the siblings. If you like what you see here, though, you can watch them together on their live summer tour. Maybe she'll do an encore?

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