Kitty Walker-McCallister is the third oldest child of William and Nora Walker, making her the younger sister of Sarah Walker and Tommy Walker and the older sister of Kevin, and Justin.
Kitty worked as a radio host, then a conservative TV pundit, whom some compared to Ann Coulter. Kitty then started working for (and eventually married) Senator Robert McCallister.
Kitty is estranged from her mother, but returns home in the first episode for the sake of her brothers and sister. She tends to share a close relationship with Sarah.
She also appears to have an okay relationship with her dad, William. William died at a family reunion on her birthday. After his death, Nora and her children discovered that he had had an affair with Holly Harper, who he believed had bore him a daughter, Rebecca, in secret.
Kitty begins the series living in New York with her long-term boyfriend Jonathan, who proposes. After she is offered a job on a political talk show 'Red White and Blue,' she considers moving back to California, which causes strain in their relationship. After a lot of flirting, Kitty then sleeps with her co-host, Warren, which ends her engagement with Jonathan, and she moves back in with her mother. This causes unresolved issues between them to resurface, such as, Nora blames Kitty for Justin's decision to enlist in the war. Although she and Warren try to begin a relationship, they hit many obstacles and eventually end things.
When Kitty met senator Robert McCallister for the first time, her brother had just been called back to Iraq, so she desperately asked the senator for help in exchange for not asking him about his divorce. The senator declined, but Kitty still felt the need to tell the public why she didn't ask the senator about his divorce and she wanted to apologize. So she said that on her last television show, her honesty impressed the Senator, who then offered her a position as his communications director which she accepted.
When she first starts her new job, all her co-workers believe that Kitty and the Senator are sleeping together. This makes Kitty feel very awkward so she applies to a dating website to find a boyfriend. On the day of her date, Robert phones the dating company. Therefore, Kitty ends up on a date with the Senator, much to her dismay. Quickly, there developed a connection between both of them and after some reluctance from Kitty's side, they got together.
Robert and her began facing problems early on, like her brother Kevin's hostlity and the public's negative opinion. After a helicopter crash which happened at the beginning of Robert's presidential campaign, Kitty gets very emotional and accidently proposes to Robert. After realising what she had done, she immediatly takes back her proposal through embarrassment but later on Robert tells her that he cannot accept her proposal until she accepts his.
While still being engaged and with Robert's campaign still at the very beginning, Kitty finds out she is pregnant with Robert's child, but doesn't tell him right away because he is so busy. Kitty is scared about the baby because this may jeopardise Robert's presidential campaign.
When he finds out, he is shocked and angry that he is the last one in the room to know. Kitty is really happy about the accidental pregnancy but Robert is unhappy wth the timing so he lies and says that he's happy about it. So Kitty organises a shotgun wedding in order to spare the senator a child out of wedlock. Before this wedding happens, however, Kitty discovers at her first sonogram that she has miscarried. She is devastated and Robert feels not only sad but guilty feeling like he was responsible because he hadn't been happy about it from the beginning. But later on they realize they want to have another child, so after a beautiful wedding ceremony they try in-vitro-fertilization, which fails.
So they decide to look into adoption which after a long and difficult process works and they happily adopt Evan McCallister. The day he was born, Robert has a heart attack the same day and misses his son's birth which makes it an extremely unimanagable day for Kitty. After Robert's heart attack, Kitty finds herself dealing with trying to take care of Evan and Robert which leads her to seek solace in the arms of another man-a single father named Alec Taylor. Kitty ends up kissing Alec and secretly visiting him. Although, they never have sex. Whilst helping Alec buy a house, they are involved in a car accident. Consequenlty, Robert finds out about them. Upon finding out about them, Robert forces Kitty to make a choice between him and Alec with Kitty ultimately choosing Robert but their marriage is damaged.
Kitty finds out as she is trying to fix her marriage, that she has cancer. Lymphoma to be exact.
After she tells Robert that she is sick he forgives her for having an affair and says that they will do whatever it takes to be N.E.D (no evidence of disease). She attempts to act normal, but the cancer takes it toll on her. She begins to lose her hair due to kemo treatments. She becomes weaker and weaker.
At Justin and Rebecca's beach wedding she dramatically passes out. She is rushed to the hospital where she has to make some tough and quick decisions on her future treatment. She decides to have a bone marrow transplant, if she can find a doner in time. None of her family members are a match. However, miraculously her half iligitament brother, Ryan is a match. At first he is reluctant to go through with the surgery, exclaiming that he doesn't owe this family anything. He then decides to go through with it out of guilt. By the end of the episode it is revealed that the surgery was a success and Kitty is now in remission. Which she is most happy about as she can live to take her son to school and watch him grow.