Name: Katherine Grey

Nickname: Kath. Kat. (Most) Kitty. Kitten (Tobi)

DOB: 1978

Age: 27 (S1)

Cast: Olivia Wilde

Family:

Tobias 'Tobi' Hudson (Fiance)

- Jeremy Renner

Nicolas 'Nico' Grey-Hudson (Son)

- Raphael Alejandro

Meredith Grey (Twin sister)

Lexie Grey (Half-sister)

Molly Grey-Thompson (Half-sister)

Maggie Pierce (Half-sister)

Ellis Grey (Mother)

Thatcher Grey (Father)

Unknown Aunt

Susan Grey (stepmother)

Laura Grey-Thompson (niece)

9 nieces

6 nephews (one deceased)

Bio:

When Katherine was young, her father, Thatcher, would bring her and her sister, Meredith, to Seattle Grace Hospital to visit her mother, Ellis, at work.

The Twin's parents had a troubled marriage, though part of this was due to Ellis spending too much time working and normal everyday problems. But a large part was due to the fact that for years, Ellis had been involved in an affair with one of her colleagues and best friends, Richard Webber. Their marital issues proved too great, and eventually Thatcher left the home when the girls were five years old. He tried to visit them on several occasions, but he got nowhere. Eventually, he stopped seeing his daughters and subsequently started a new family with his new wife, Susan Grey, and had two children.

When Thatcher left Ellis, she continued her relationship with Webber, although he still had a wife, Adele. Although Richard tried to conceal his relationship with Ellis, Adele always knew, so if she was in their company, she would just play with Katherine and Meredith. Eventually, Richard broke off his relationship with Ellis, as he felt he was being the better man, by walking away from Ellis, with Katherine and Meredith only meters away, riding on a carousel. Katherine vaguely remembered her mother's pregnancy with Webber's child after he broke it off. In the memory, Ellis made it clear that she did not want to even look at the child. Shortly thereafter, Ellis accepted a fellowship opportunity at Massachusetts General Hospital. She relocated to Massachusetts with Katherine and Meredith, and Thatcher lost all contact with his daughters. As an adult, Katherine's only childhood memory of Thatcher was giving her cereal in the morning.

Katherine went to college at Harvard and graduated with honours (Unlike Meredith at Dartmouth, despite excessive drinking and partying, she graduated) Following their graduations, Ellis suggested that Meredith find another direction in her life, not being convinced that she had what it took to survive medical school and make it in the surgical world, unlike Katherine.

Following an argument about Meredith's future, she spent two months traveling in Europe with her best friend Sadie Harris, who also hated Ellis. But during that time, Ellis Grey was diagnosed with early-onset Alzheimer's disease and Katherine had her placed into a nursing home in Seattle when she struggled to look after her mother and her own son alone.

After graduating from medical school, Katherine moved back to Seattle from Massachusetts, and into her childhood home with her son, Nico, (At the same time Meredith moved from Boston) in order to begin their internship at Seattle Grace. Katherine and Meredith are the only ones who know about their mother's condition outside the nursing home staff, whose personnel were bound by contract to keep Ellis's condition confidential, and Katherine's fiancee Tobi. Ellis also made the twins promise not to tell anyone.

Personality

Katherine is level headed, bright, enthusiastic, and generally not afraid to speak up when she thinks she is right. She has good relationships with patients, and it is shown she isn't as judgmental as her colleagues.

She deeply loves her son, and has worked hard being, technically, a single mother, despite Tobi being part of Nico's life, his career as a military man means he has spent more time away from his son than with him. Katherine and Tobi have been engaged for almost as long as they have been together, but are both comfortable with their relationship as it is. They both love one another, and their son, and feel like there isn't a rush to get married.

Notes and Trivia:

Katherine does not like big weddings.

Her favorite ice cream is chocolate ice cream.

Her blood type is AB.

Katherine hates it when people change channels during the commercials.

She knows how to swim.

She does not play video games.

According to Chief Webber, Katherine has the best surgical skills. This is later reinforced by Callie agreeing with him.

Katherine is happy and cheerful when she is hopped up on morphine or drunk.

Katherine is a very intuitive surgeon with a natural flair for medicine.

Her mother and Richard Webber met when she was three.

She is Richard Webber's and Meredith Grey's medical proxy.

She had 7 letters of recommendation for her internship at Seattle Grace Hospital.

Katherine loves Chinese food.

Her favorite Christmas gift was a suture kit.

Her emergency contact is Meredith Grey and vice versa.

She is not a Bush supporter

She hates rhubarb

Pairing:

As I don't know when Katherine and Tobi end, it's hard to plan hospital romances, I can either have Tobi having died pre-season 1, and a lot of season 1 is her dealing with that death or he dies at some point, either in season 1 or season 2 or something like that.

Alex Karev (After Izzie leaves/On and off/Weaved with Izzie (When he's on with her, he's off with Katherine, and vice versa)) 

or Mark Sloan (Up until his death)

Owen Hunt (Endgame)