Julianne Hough Officially Joining Brother Derek on 'World of Dance' (Exclusive)

Julianne joins the NBC series as a 'mentor' for season two, and says she's not returning to 'Dancing With the Stars.' The 29-year-old, who has teamed up with the 'SpeakENDO' campaign to spread awareness about Endometriosis, says she's also planning on returning to music -- and has a television series of her own in development.