'House of the Dragon': Milly Alcock, Emily Carey join HBO series

July 6 (UPI) -- Milly Alcock and Emily Carey have joined the cast of House of the Dragon.

HBO confirmed Tuesday that Alcock and Carey will have roles in the Game of Thrones prequel series.

Alcock will play a young Princess Rhaenyra Targaryen, with Emma D'Arcy to portray an older version of the character. Rhaenyra is the first-born child of King Viserys I Targaryen (Paddy Considine).

Carey will portray a young Alicent Hightower, played by Olivia Cooke. Alicent is the daughter of Otto Hightower (Rhys Ifans), the Hand of the King, and "the most comely woman in the Seven Kingdoms."

"the most comely girl in court has ARRIVED," Carey tweeted Tuesday.

Other cast members include Matt Smith as Prince Daemon Targaryen and Steve Toussaint as Lord Corlys Velaryon.

House of the Dragon is based on George R.R. Martin's book Fire & Blood, which recounts the history of House Targaryen. The series is set 300 years before the events of Game of Thrones.

House of the Dragon is created by Martin and Ryan Condal. Condal and Miguel Sapochnik will serve as showrunners and executive produce with Martin, Vince Gerardis, Sara Lee Hess and Ron Schmidt.

HBO is also developing three more Game of Thrones spinoffs, 9 Voyages, aka Sea Snake, 10,000 Ships and Flea Bottom.

Game of Thrones aired for eight seasons on HBO from 2011 to 2019. The series is based on Martin's A Song of Ice and Fire book series.

Alcock is known for the series Reckoning, Upright and The Gloaming. Carey played a young Diana Prince in Wonder Woman and Grace Beauchamp on Casualty.