Credit: Frazer Harrison/ Getty Images, Michael Buckner/Getty Images Photo: Derek Hough vs. Julianne Hough: Which DWTS Pro Is Older? (PHOTO)

You watch Derek Hough shake it in the ballroom each week on Dancing With the Stars and you've seen his sister Julianne Hough make her mark as a pro, movie star, and even Dancing With the Stars guest judge, but do you know which of these blondies was born first? We've got the answer, and it might not be what you expect.

Believe it or not, Derek is three years older than his sister!

Derek was born on May 17, 1985, making him 28. Julianne, on the other hand, was born on July 20, 1988, making her 25 years old. 

Maybe it's her mature red carpet looks, her insightful judging, or her successful movie career, but we always think of Julianne as being the older of the sibs, though obviously that's not the case. Even though we know the right answer, we keep thinking it's the other way around!

Are you surprised, or did you totally know that Julianne was younger than her big bro? Sound off in the comments below!