Season 1 (2006–07)

Main article: Brothers & Sisters (season 1)

Most of the season focuses on The Walkers dealing with the loss of William Walker and the secrets uncovered by his death, most notably the discovery of Holly Harper, a woman he had an affair with, and her daughter Rebecca. The season also introduces the audience to the lives of the Walker siblings who must deal with their jobs, turbulent love lives and each other.

Season 2 (2007–08)

Main article: Brothers & Sisters (season 2)

The second season focused mainly on the romantic lives of the Walker siblings. As Kitty and Robert start planning their wedding, Kevin runs into Scotty (his lover from the first season) and they become a couple. Sarah must now deal with her divorce and being a single parent while Tommy and Julia go through serious issues after struggling with the loss of one of their twins. Nora begins a new romance with one of Robert's staff and, along with Rebecca, tries to help Justin regain his life after being injured in the war.

Season 3 (2008–09)

Main article: Brothers & Sisters (season 3)

After the discovery that she is not, in fact, a Walker, Rebecca must deal with her new place in the family and her new relationship with Justin which could be in trouble with the appearance of Ryan—William's actual secret child. Kitty and Robert face problems in their marriage as they try to adopt a baby while Kevin and Scotty settle into married life. Nora decides she wants a career of her own after spending most of her life in the back seat and finds a new romance. With Holly becoming a major presence at Ojai, Saul and Sarah decide to quit leading to a new business venture for the eldest Walker sibling, while Tommy turns to drastic measures to take back the family business.

Season 4 (2009–10)

Main article: Brothers & Sisters (season 4)

The show was renewed for a fourth season on April 23, 2009.[5] It premiered on September 27, 2009 on ABC.[6]

This season sees Kevin and Scotty decide to start a family while Kitty finds her family may be torn apart when she receives unexpected news that she has lymphoma, cancer of the lymph nodes. Sarah finds love with Luc, a man she met in France who traveled to America to be with her, but the dream doesn't seem to last in her real life. Justin is finding it hard to balance his engagement to Rebecca with his medical school studies, while Rebecca has troubles of her own. After not having their wedding Rebecca comes to find out she is now pregnant with Justin's baby but Rebecca ends up having a miscarriage which causes some more strain on their relationship. While her children go through difficult times Nora must try her hardest to get them through their troubles and Ryan causes trouble for the Walkers and Ojai by teaming up with a man from William's past. Will Holly's obsession with the secrets of Ojai ruin her relationship with David? The season ends with a horrific car crash that leaves Holly severely injured and the fate of Senator Robert McCallister unsure.

Season 5 (2010–11)

Main article: Brothers & Sisters (season 5)

Brothers & Sisters was renewed for a fifth season on March 5, 2010.[7] It premiered on September 26, 2010 on ABC. The events of the fifth season begin one year after the season 4 finale.[8]

The season starts with Kitty holding on to Robert who has been in a coma since the accident when she is faced with the decision of whether or no to turn off his life support. Sarah considers selling the new land and water found in Ojai to start a new chapter with Luc. Kevin, who has become a low-paid pro-bono lawyer, and Scotty begin the adoption process after their surrogate, Michelle, appears to lose their baby. Saul bumps into an old flame, Jonathan, who now campaigns for a HIV+ charity, and reveals that it was Jonathan who infected Saul. Justin and Rebecca struggle to reconnect after his year abroad leaving her feeling abandoned and questioning her future. Meanwhile, Holly has developed long term memory loss after the accident and is struggling to remember her life and loved ones.[9]

Finally, Nora has become distant from her family whilst she searches for a new career and purpose when a unique job opportunity presents itself at a local radio station. Later in the season, Nora's first love, Nick Brody, returns with a revelation that could change the Walker family forever.