Julianne Hough had a surprise guest at her recent AOL Music Sessions taping: her big brother, Derek. The fellow 'Dancing With the Stars' pro dropped in to perform 'Dreaming Under the Same Moon,' a song he also lends his vocals to on his little sister's debut album. (Watch the video below.)

"We work so well together," Julianne told The Boot of working with her brother. "We performed together growing up ... so we collaborate really well and obviously blend well because we're family."

The Hough siblings joke that they were nicknamed the 'Blonde Osmonds' when they were younger, as their entire clan of five towheaded brothers and sisters often performed together. Buy 'Dreaming Under the Same Moon' on iTunes