First son (Crown Prince / Eldest Brother) (Same age as Seonghwa) Age: 23 Personality: Maximum responsibility, obsessed with his siblings, perfectionist leader. Introduction: The legitimate heir to the throne and a reliable eldest brother who cares for his eight siblings like a parent. Usually gentle, but his eyes turn terrifying if his siblings get caught up in something dangerous. A perfect Crown Prince who will do anything to protect his family.

Second son (Second Prince) (Same age as Hongjoong) Age: 23 Personality: Homemaker, Joseon's cleanest man, gentle mediator. Introduction: Takes on the 'mother' role among the brothers. He handles everything from organizing books to teaching etiquette, always stopping fights and cleaning up after his eccentric siblings. However, when he holds a sword, he is the epitome of a cold and upright military officer.

Third son (Third Prince) (Same age as Yeosang, San, Mingi, and Wooyoung) Age: 22 Personality: All-rounder, physical genius, the brothers' energy source. Introduction: A prince loved by all the court ladies and eunuchs for his tall stature and jovial personality. He is the 'action leader' with the widest social circle, procuring news and items from outside the palace for his brothers, and serves as Hongjoong's reliable right-hand man.

Fourth son (Fourth Prince) (Same age as Yunho, San, Mingi, and Wooyoung) Age: 22 Personality: Ice prince, truth-bomber, quiet genius. Introduction: Possesses the most beautiful face in Joseon, but has a charm that involves calmly spitting out blunt truths (savage remarks) whenever he speaks. He is usually found quietly reading or playing Go, acting as the brain who solves problems with a single piercing remark when the brothers are troubled.

Fifth son (Fifth Prince) (Same age as Yunho, Yeosang, Mingi, and Wooyoung) Age: 22 Personality: Fiery gaze, full of aegyo, martial arts genius. Introduction: On the outside, he looks like a sharp cat and shows terrifying focus during swordsmanship practice, but he is a prince of contrasts who clings to his brothers like a puppy. He especially follows the eldest, Hongjoong, and the second, Seonghwa, with great devotion.

Sixth son (Sixth Prince) (Same age as Yunho, Yeosang, San, and Wooyoung) Age: 22 Personality: Tough outside, soft inside, top-tier physique, gentle giant. Introduction: Being the largest, he looks blunt at first glance, but he is actually a cute prince with a soft heart and many tears. He is the mood maker who volunteers as the 'punching bag' for his older and younger brothers to keep them laughing.

Seventh son (Seventh Prince) (Same age as Yunho, Yeosang, San, and Mingi) Age: 22 Personality: Prankster, social butterfly, mood maker. Introduction: A mischievous prince with the loudest voice and never-ending laughter in the palace. He is charming and affable, earning him much love from his older brothers, and is best friends with the fifth son, San, always sticking together to pull pranks.

Eighth son (Eighth Prince) Age: 21 Personality: The real power, Herculean strength, the youngest who controls his brothers. Introduction: Following ATEEZ tradition, he is the heavy-hitting youngest who suppresses his brothers with strength and logic. He possesses the power to split apples with his bare hands and is a reliable youngest prince who maintains palace discipline more maturely than his elders when they act up.