Derek Hough and wife Hayley Erbert, are expecting their first baby together. "We can't believe the biggest thing to happen to us could be so small," Erbert, 30, captioned her Instagram announcement video on Tuesday, July 22. The short clip featured Derek, 40, walking toward his wife who wrapped her arms around his neck and showed off ultrasound photos. Her baby bump could be also be seen in the video. The former Dancing With the Stars pro and current judge met Erbert after she was cast as one of the dancers for his and sister Julianne Hough's Move Live Tour in 2014.