Derek Hough, Julianne Hough Derek Hough, Julianne Hough

Derek Hough has spoken out about his sister Julianne's blackface Halloween costume.

"She's so apologetic," he told E! News. "She's so, so sorry and I just hope that we can all forgive her and move on. ... Obviously, it wasn't her brightest moment in her life."

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Derek says Julianne is "mortified" at the backlash she received for wearing blackface when she dressed as Crazy Eyes from Orange Is the New Black over the weekend, and that the Dancing with the Stars alum never intended to offend. "She's my little baby sister and she's the sweetest thing ever. She is just beyond beside herself," Derek said.

Julianne apologized for her costume gaffe on Saturday. "I am a huge fan of the show Orange Is the New Black, actress Uzo Aduba, and the character she has created. It certainly was never my intention to be disrespectful or demeaning to anyone in any way. I realize my costume hurt and offended people and I truly apologize," she wrote on Twitter.