Jung Yunho      25 years old

Young CEO of Shine Architectual

Eldest son of Jung Sang Kook

Jung Changmin      23 years old

Yunho's younger brother

Later known as Shim Changmin

Kim Jae Sun (Koo Hye Sun)      25 years old

Eldest daughter of Kim Sung Il

Jaejoong's sister

A model

Kim Jae Joong      18 years old

Art student of Seoul University

Youngest son of Kim Sung Il

Kim Hyun Joong      20 years old

Law student of Seoul University

Jaejoong's boyfriend

Kim Junsu      24 years old

Young CEO of MS Automobile

Jaejoong's cousin

Park Yoochun      25 years old

Young CEO of YH Telecomunication

Yunho's best friend

In love with Kim Junsu

Cho Kyuhyun      18 years old

Art student of Seoul University

Jaejoong's classmate and best friend