Hough, 25, is currently taking part in the 11th season of the US celebrity dance show and is partnered with Dirty Dancing star Jennifer Grey.
His sister Julianne, who is also a professional dancer and has appeared on eight seasons of the show, did not return for the new series as expected.
But Hough explained that her absence is due to her work commitments with the movie remake of Footloose.
He said to Extra: 'Julianne was gonna be back this season, but there were conflicts with the movie Footloose that she's doing right now.'
He added: 'There was a short overlap and it just couldn't work it out. But she's doing great, so I'm excited for her.'