Katharine Anne "Kitty" McCallister (Calista Flockhart) is the second eldest child of the Walker family on the TV show "Brothers & Sisters." At the start of the show, Kitty was a radio host in New York, who was offered a chance to be part of a political show in Los Angeles called "Red, White & Blue". This caused problems in her relationship with her fiance, Jonathon (Matthew Settle), who didn't want her to move to LA.

This relationship broke down shortly before her father William Walker (Tom Skerritt) suddenly died and Kitty, along with the rest of her family, discovered that he had been cheating on her mother Nora (Sally Field) and embezzling money from the company pension fund, jeopardizing the future of the company. This news upset Kitty, who ended up sleeping with her co-host Warren Salter (Josh Hopkins) which made her relationship with Jonathon even more complicated as he was after a reconciliation. Jonathon went back home to New York and Kitty decided to pursue an affair with Warren, but he was already involved with his assistant Amber (Keri Lynn Pratt) and she broke it off.

Kitty's brother, Justin (Dave Annable) was called up to fight in Iraq, and fearing for him, she asked Senator Robert McCallister (Rob Lowe) to intervene when he appeared on her show, but he refused. Kitty realized she had been wrong to do so, and apologised to her guests before leaving the show. Robert was impressed by her and, after much persuasion, she began working as his Communications Director. They were attracted to each other, but due to her being on a "man fast", Kitty was reluctant to date at first. After their scheduled campaign helicopter crashed, she asked Robert to marry her. He later proposed and she accepted.

Kitty starts to plan her wedding, but then finds out she is pregnant and the wedding is moved forward to avoid a political scandal. Kitty then miscarries, postponing the wedding for a while. When they do marry, they both aim to have a child, but in vitro fertilization fails and they look into adoption asking her sister, Sarah Walker (Rachel Griffiths) to write a letter of recommendation.

While working for Robert, Kitty wrote a book about the presidential election campaign and calls in an old friend Isaac Marshall (Danny Glover) to advise about the press and Robert's political image. When Robert hears about the book, he is angry and Kitty accidentally leaves the book lying around at Nora's house. Nora and Justin read it, seeing that Kitty talks about them negatively. This leads to arguments, but Robert reads it and tells her it is good, but if published she would have to step down as Communications Director.

Eventually they find an adoptive mother, brain surgeon Trish Evans (Sonja Sohn) and after a moment of doubt, adopt her son and call him Evan. Robert then suffers a heart attack and their marriage starts to break down as he sinks into depression and starts planning to run for Governor. After flirting with a single father, Alec (Matt Letscher), her husband becomes upset. While Kitty is visiting her brother Tommy (Balthazar Getty) in Mexico he flies off thinking she doesn't love him.

Kitty is then diagnosed with non-Hodgkins lymphoma and starts chemotherapy. The family moves in with Nora so she can help out with Evan. Robert and Kitty repair their relationship, but the cancer has spread and she collapses at Justin's wedding. Kitty needs a bone marrow transplant but all of her siblings test negative except her half-brother Ryan (Luke Grimes). Ryan initially does not want to donate his bone marrow, but changes his mind. After the operation, Robert concedes his run for governor while Kitty runs for his Senate seat.

At the end of Season 4, the family is involved in a massive auto accident, and the seriously injured Robert asks Justin (a medical student) to treat the others. He lapses into a coma while Kitty stands by begging him to survive.

Memorable Quotes:

"Hamptons, 2002, broke a heel dancing on a table. Got sandwiched in between this, uh, club promoter and some tortured playwright."

"You know tonight was unusually bizarre, even for my family."