Here is a rough diagram of the character relationships.
It's like this.
Age
Kim Nam-joon, Kim Seok-jin, Min Yoon-gi, Jung Hoseok: 25 years old
Park Jimin, Min Yeoju, Bae Joohyun: 24 years old
Kim Tae-hyung: 23 years old
Jeon Jungkook: 22 years old
no see.
