Main Characters:

Kwon Jiyong

Second Prince of the Kingdom

Current King

Killed his Brother to obtain the throne

He has a complicated relationship with Taeyeon.

She, is his belief.

While he, is her family's murderer.

Obsessive, Complusive, Eager to Please, Rage Issues etc. 

To many, he is considered as insane or mentally unstable, due to his rage issues and temperaments.

Kim Taeyeon

Widow of Seunghyun, Jiyong's current Wife and Queen

Eldest of the remnants of the Kim Household

Her family was exterminated by Jiyong for promising her as wife to his brother and not to him, because both had been dating for a while before the decision to marry her to Seunghyun occurred.

Leader of SM Corps

Creator of Red Velvet

Has a deceased son

For a long while, she was the light of Seunghyun's life, despite him not loving her at her and she not loving him initially.

She is the holder of Jiyong's heart, the only one he willingly listens to and has the ability to rein in his tempers, apart from Daesung.

She is the love of Jiyong's life, but Jiyong is her target of hatred and revenge because he forcefully aborted her unborn child and killed her entire family

Kwon Royal Family

Youngbae

Third Son of the Royal Family

Has a daughter named Chaeyin from his first marriage (His wife died)

He has a crush on Yuri

Silent, Brooding, but the most Matured and Levelheaded

Kwon Chaeyin

The seven year old daughter of Youngbae from his first marriage

Likes her Aunt Yuri and Taeyeon a lot

Is tired of her Father not seeing that he should chase Yuri and hence cooks up her own plans to make them meet as reguarly as possible

Does not like Jiyong since he bullies her

Kim Family Household/ SM Corps

Jessica Kim

Previously known as Jung Soo Yeon

Second Eldest of the Kim Girls

Adopted by Soo Man, Taeyeon's Father

Specialises in Weaponry Combat and Political Prowess

Cold, Calculative, Easily Annoyed, Pragmatic, Sly

Sistercon

Sunny

Otherwise known as Kim Sun Kyu

Third Eldest of the Kim Girls

Taeyeon's Cousin 

Has been living with Taeyeon since they were five years old

Specialises in Communication and Information Gathering

She is the only one able to hold and get information out of drinkers, since Taeyeon and all other members are alcohol trashes

Quiet, Listener, Taeyeon's trusty confidant

Tiffany Kim

Previously known as Hwang MiYoung

The Fourth Eldest

Specialises in Networking and Information Gathering

Owns a Fashion Boutique which she uses to gather information from higher classes

Adopted by Soo Man

Closest to Taeyeon apart from Sunny and Soo Yeon

Warm, Bright, Overly Energetic, Annoying [At Times]

Kim Hyoyeon

Adopted by Soo Man

Was from the Him [힘] slave race known and enslaved for their abnormal strength and physical power

Fifth Eldest

Specialises in Hand to Hand Combat and Weaponry

Brutally Honest, Violent At Times, Ardently Protective

Yuri

Previously known as Kwon Yu Ri

Sixth Eldest

Expert in Sport and Weaponry, Acrobatics

She was adopted by Taeyeon's Father from an acrobatic circus that was mistreating her due to her flexibility

Silent, Serious, Loyal and Lovely

SooYoung

Previously Known as Choi Sooyoung

Seventh Eldest

Expert in Art of Seduction and Camadarie

The oldest of the youngest three closest to Taeyeon

Owns a NightClub

Noisy, Self-Narcissistic, Hilarious

Yoona

Previously Known as Im Yoon-ah

Adopted by Taeyeon's Father

14 Years Old

Socialite and Information Gatherer Expert

Always paired with Sooyoung and Seohyun

Childish, Playful, Prankster, Highly Attached to Taeyeon

Has only been in the Kim Household for Two Years

Was adopted alongside Seohyun

Seohyun

Previously Known as Seo Joohyun

13 Years Old

Maknae

Was Adopted alongside Yoona

Kindest Soul