One Chicago’s 6 best sibling relationships

6. Kelly Severide and Katie Nolan

In Chicago Fire season 2, we were thrown a curveball in the introduction of Severide’s half-sister, Katie Nolan (Brittany Curran). Katie is introduced in “A Power Move” outside a café talking with Severide’s father Benny (Treat Williams), much to Kelly’s surprise. Severide confronts her in the later episode “No Regrets” and finds out that she is, in fact, his sibling.

After he first accused her of being in a relationship with Benny, it’s no surprise that Katie is apprehensive about meeting further with her newfound brother, but that soon changes. Since she’s a student at culinary school, Severide invites her to cook for the firehouse, and Katie eventually agrees.

During her time at Firehouse 51, Katie also shows a romantic interest in Brian “Otis” Zvonecek (Yuri Sardarov), much to Severide’s annoyance. He turns on the big brother protective mode and tries to intimidate the funny man of the firehouse.

But not only is Severide protective of his sister, but he is also remarkably supportive and becomes the only family member to turn up to Katie’s graduation from culinary school—another reason to love their relationship further. Unfortunately, things soon go south for the half-siblings.

In “Tonight’s The Night,” Katie gets kidnapped by Vince Keeler (guest star Jake Weary), who is seeking revenge on Severide for humiliating him at the firehouse. In the next episode, she is found beaten and bruised. In a devastating blow to Severide, Katie then decides to leave Chicago to take a job in another state and departs with some loving words for her half-brother.

Although they had only known each other for a few weeks, the relationship between Severide and Katie is as strong as any sibling relationship could be. Severide looked out for his sister both with Otis and in the kidnapping ordeal. Who knows where One Chicago would have taken them if she had stuck around for a little longer?