What did Dancing With the Stars pro Derek Hough think of his sister, Julianne Hough, performing in Fox's Grease: Live?

How 'Dancing With the Stars' Prepared Julianne Hough To Take On 'Grease Live'

Julianne had the lead role of Sandy Young in Sunday night's Grease: Live. Derek dutifully watch the special with a group of friends and documented his feelings on Instagram.

Filming his sister in the special, Derek yelled out "Yeah girl!" He wrote in the caption of the video: "Killin it ! #GREASELIVE my Sister ! Proud as a mutha".

Julianne Hough Talks Why Brother Derek Is Still Single

 Killin it ! #GREASELIVE my Sister ! Proud as a mutha

A video posted by Derek Hough (@derekhough) on Jan 31, 2016 at 7:19pm PST


In the next video, Derek said he was "straight up emotional right now," yelling out, "That was beautiful, Julianne! So proud of you!"

Singing live for all to hear!!!! Nailed it! #emotional #proudbigbrother A video posted by Derek Hough (@derekhough) on Jan 31, 2016 at 9:08pm PST

Many Fox viewers were just as impressed, with 12.18 million viewers tuning in for the special. While it was not able to top NBC's broadcast The Sound of Music Live!, it did best both Peter Pan Live! and The Wiz Live! in ratings.

Deadline reports that Grease: Live gave Fox their best ratings in the 18-49 demographic and total viewership since the season 2 premiere of Empire back in September.

Meanwhile, Julianne is expected to return to her role as permanent judge on Dancing With the Stars next month, alongside Carrie Ann Inaba, Len Goodman and Bruno Tonioli. It is unknown if Derek will return as a pro, but his big win with Bindi Irwin last season suggests the viewing audience loves him, so DWTS producers will likely want him to return.

Dancing With the Stars season 22 premieres Monday, March 21 at 8 p.m. ET/PT on ABC.

Tags: Dancing with the Stars Reality TV ABC Grease Live!