The 32-year-old dancer also revealed who he's rooting for this season.
Derek Hough supports his sister no matter what she decides to do in her career.
ET's Katie Krause spoke with the 32-year-old dancer at the Entertainment Weekly Pre-Emmy party at Sunset Tower on Friday, where he opened up about Julianne's decision not to return to the judging table for season 25 of Dancing With the Stars.
"We were supposed to go back on tour, she's just newly married, she is a very focused woman," Derek revealed. "She has her sights set on other opportunities and other things."
"Sometimes you just gotta step away from something for a little bit to create those opportunities," he continued. "She's Julianne, man. She's a beast."
While the ballroom will be Hough-less this season, Derek's pal, Mark Ballas, is returning to the show after taking two seasons off.
"DWTS, I feel like everyone brings something to it. It's like different seasonings, and I think that that past two seasons we've missed Mark's spice," Derek, who was the best man at Ballas' wedding last year, confessed. "We've missed his spice. We've missed his dynamic. We need that."
Though Ballas has a special place in his heart, Derek insisted he's remaining un-biased this season, and is "rooting for everybody."
"I love them all. I was just nominated for an Emmy this past weekend, and it's always been for Dancing With the Stars, so it's kind of bittersweet, because it was my last performance," he admitted. "I love that show. It's amazing."
"I'm never saying never [to returning to the show in the future]," he added. "They're my family. I will always be a positive ambassador for that show. I love it dearly."
"But I know [Ballas' partner] Lindsey [Stirling], I've worked with her before. She's amazing and so I'm rooting for them," he confessed. "They're incredible people. Great people, creative, great competition."
See more in the video below.