Synopsis by Soompi: Based on the manhwa (Korean comic) of the same name, “The King’s Affection” will tell the story of a pair of royal twins, one male and one female. Although the sister is initially abandoned for being female, she later disguises herself as a man to become the crown prince when her brother dies.
The drama airs from October 11th onwards on KBS and Netflix!
Park Eun Bin as Crown Prince Lee Hwi
SF9's Rowoon as Jung Ji Woon, the crown prince's teacher
Nam Yoon Su as Lee Hyun, a royal family member
VICTON's Byung Chan as Kim Ga On, Lee Hwi's bodyguard
DIA's Jung Chaeyeon as Noh Ha Kyung, the youngest daughter of the Minister of War
Bae Yoon Kyung as Sin So Eun, the only child of the Minister of Personnel
Source: The Swoon, Newsen (1, 2) & KBS (1, 2) all via Soompi 1, 2, 3
I am a sucker for this trope and love both leads so I'll definitely be watching lol