ABC released the stills for Grey's Anatomy season 10, episode 11 Man on the Moon as well as the synopsis for episode 12 Get Up, Stand Up.

Both episodes center around preparations for April Kepner's wedding starting with Man on the Moon featuring the Kepner family. Viewers will meet April's sisters for the first time as they arrive in Seattle to help her with wedding arrangements. However, they will prove to be more trouble than helpful.

The three siblings will be played by Days of Our Lives' Emily Happe, Drop Dead Diva's Elizabeth Bond and The Middle's Grace Bannon. 

Things will get awkward when Jackson Avery and Matthew have to work together, and April and Jackson are also forced to team up while operating on a patient.

Man on the Moon airs Thursday, Dec. 5, at 9 p.m. ET. Its official synopsis is below.

"April's sisters arrive to help celebrate April's upcoming nuptials and quickly get on her nerves. Matthew and Jackson are forced to work together when they witness a terrible accident, Callie and Arizona work hard to reestablish their relationship and Cristina is pressured to live stream an upcoming surgery. Meanwhile, a familiar face returns to the hospital."

The synopsis for episode 12 -- Get Up, Stand Up -- reveals a life-altering moment for Derek Shepard. April's wedding will also take place in the respective episode, which is the series' last before it goes on a winter hiatus. Leading up to actress Sandra Oh's exit from the series, her character, Cristina Yang, continues to be at odds with once best friend Meredith Grey.

"On the day of April's wedding, the Grey Sloan Memorial doctors are all preoccupied with their own drama. Meredith and Cristina continue to argue about their research and careers, Bailey comes clean to Ben about her feelings regarding him moving back to Seattle, and Shane puts himself in a risky situation. Meanwhile, Derek gets a phone call that will change his life, on the winter finale of Grey's Anatomy."

Scroll through the photos to see stills from Man on the Moon.