Kim Jaejoong

Age:19

-Ran away from his house after discovering he's pregnant with his professor's baby

-Looks cute but he is rude 

-Currently living with his husband (professor) Jung Yunho

-Eldest of of the three; siblings are Junsu and Onew

-Hates Onew for having a perfect rich life unlike him

Kim Onew

Age:18

-Spouse to the wealthiest business man, Shim Changmin 

-Married Changmin to save his father

-Abused badly by his husband

-Clumsy and cute but he has breathing problems

-Adored by his parents for his good grades

Kim Junsu

Age:16

-Engaged to Park Yoochun due to his parents' wish

-Confident and cute but is always bullied by everyone

-Tries to unite his brothers but fails almost every time

Jung Yunho

Age:27

-Professor; married his student Jaejoong

-An orphan 

-Struggled in life to achieve his current position

-Loving and caring person

Shim  Changmin

Age:27

-Owner of Shim Corporation

-Married Onew due to his father's wish

-Uses Onew as his puppet; very dominating

Park Yoochun

Age:27

-Manager of Shim Corporation

-An intelligent young man

-Truly cares for Junsu

-Hates to see Junsu always trying to unite his brothers

-Loves Junsu but hates his childish ambitions

Kim Heechul and Kim Siwon

-Parents of Jaejoong, Onew & Junsu

They love their children equally but they are always looked down by Jaejoong.

Siwon has brain tumor and he cannot live long so he wants to see his sons get married early before his death. He is a caring and a loving father.

Heechul always stands by his husband. He adores Onew more than his other sons because Onew is clumsy and has breathing problems, but Jaejoong and Junsu have always taken that in a negative way. Junsu understood Onew's condition but jaejooong never understands.