"Happy Birthday to this handsome man of mine. I love you," Erbert, also a dancer, captioned a photo of herself kissing Hough.
Julianne Hough shared a series of throwback photos and a lengthy post on her own account.
"Happy Birthday to my big brother!" the 28-year-old dancer wrote.
"I'm so lucky to be your little sister and to have had you to look up to my entire life. You never cease to amaze me with your talents, gifts and your heart!"
"We have had so many adventures together in this journey we call life. Great ones, scary ones, tough ones, fun ones and hilarious ones. But just know I can't wait to do all the adventures with you!" she added. "I love you so much Derek!"
Copyright 2017 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.