James is the oldest member of CORTIS, born on October 14, 2005. Although Martin is the official leader, James has a naturally responsible and organized presence. He can be very involved in making plans, keeping track of what the members need to do, helping everyone prepare before schedules, and making sure things are organized. He may remind the members when it's time to sleep or get ready, help calm everyone down when they're being too energetic, and make sure nobody forgets their belongings when they're packing. He is also heavily involved in choreography and performance, as well as CORTIS's creative work.

Martin is the leader of CORTIS and is involved in the group’s music and creative work. He participates in songwriting and production and is also involved in choreography and visual content. As the leader, he has an important role in keeping the members together and helping guide the group creatively. He is the oldest? No—James is the oldest, while Martin is one of the older members. Martin was born on March 20, 2008.

Seonghyeon was born on January 13, 2009. He is involved in CORTIS's music and creative work, including songwriting and production, and contributed to both “FaSHioN” and “Lullaby.” He participates in the group's performances and creative development and works with the other members on their music and visual concepts. He is one of the younger members of CORTIS and contributes to the group's collaborative approach to creating music and performances. His usual nickname is "sean"

Juhoon was born on January 3, 2008 and is a member involved in CORTIS's music, performance, and creative process. He has songwriting and production credits and contributed to the group's creative work, including “FaSHioN.” He is part of the group's collaborative process, where the members participate in creating rather than simply receiving everything from outside producers. He works alongside the other members in rehearsals and performances and contributes his own ideas to the group's music and artistic direction.

Keonho was born on February 14, 2009 and is the youngest member (maknae) of CORTIS. He participates in the group's music and creative process and has contributed to their choreography and visual work. He also contributed to “FaSHioN.” Because he is the youngest member, he has a different place within the group's age dynamic, but he is still an active contributor rather than simply being treated as the group's youngest performer. He works with the other members on music, choreography, performances, and visual content.