Pokgun Oppaga Sesiraeyo

A curse affects the Ascania imperial family, causing each member to be killed by someone they love, with the only way to break it being the birth of a female heir. When a slave girl with distinctive, color-shifting eyes is found, she is named Princess Chloe and becomes the sister of three princes. Eager for a family, she finds her new brothers to be somewhat unusual. They have long had to suppress emotions to protect themselves, but Chloe's presence may begin to alter their hearts.