NINE.i is composed of 10 members born between the late 1998 and early 2004. Their names are: Jewon, Winnie, Eden, Vahn, Vari, Seowon, Taehun, Joohyoung, Jiho, and Minjun. The oldest member is Eden (Mar 27, 1998) and the youngest member is Jiho (born Aug 10, 2004).
Some of the members were known to the public prior to their debut because of their participation in different idol survival shows. Vahn was part of Under Nineteen; Minjun was in Wild Idol; Jewon was in Produce X 101.
Ages from oldest to youngest:
| Member | Birthday |
|---|---|
| Eden | Mar 27, 1998 |
| Winnie | Nov 18, 1998 |
| Jewon | Dec 30, 1998 |
| Minjun | Feb 26, 1999 |
| Vahn | May 7, 1999 |
| Vari | Sep 3, 2000 |
| Seowon | Dec 18, 2000 |
| Taehun | Mar 21, 2002 |
| Joohyoung | Mar 15, 2003 |
| Jiho | Aug 10, 2004 |
