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Matthew Casey and Sylvie Brett's Relationship History on Chicago Fire

Revisit some of "Brettsey's" cutest moments over the years on Chicago Fire

By Megan Lasher
Brett Saves a Man Who’s Been Shot with an Arrow | NBC’s Chicago Fire

There's nothing One Chicago fans love more than seeing two Chicago heroes fall in love. And when it comes to Firehouse 51, there's one fan-favorite pairing whose slow burn romance left audiences with a lot of hope. 

How to Watch

Watch Chicago Fire on NBC and Peacock.

Chicago Fire's Matthew Casey (Jesse Spencer) and Sylvie Brett (Kara Kilmer)—lovingly called "Brettsey" by fans—have had a complicated platonic and romantic history. 

The duo were friendly from the beginning of Season 3, when Brett first arrived on the Chicago team. They were connected through Gabby Dawson (Monica Raymund), who ultimately married and later divorced Casey. Because of her friendship with Dawson and Dawson's relationship with Casey, Brett intentionally did not pursue anything more than a casual friendship with the Truck 81 leader.

However, after the end of his marriage and in the wake of Dawson's departure, Casey was dealing with his broken heart and he and Brett became much closer, leading to the genesis of "Brettsey." 

Here are some of the most beloved highlights from Casey and Brett's complicated, close-knit relationship: 

Brett and Casey Bonded Over Both Missing Dawson

After Dawson moved to Puerto Rico, Brett approached Casey and asked, "How could you just let her go?" Casey told her that he's even more upset than she knows. When Brett bemoaned that she "didn't even get to say goodbye," Casey gave her an old picture of her and Dawson that Dawson left for her.

"Love you, partner. Always will," Dawson had inscribed on the back. 

Casey Tried to Ask Brett to Dinner

In the dramatic Season 7 finale, we saw a few potential Brettsey teases.

Casey saved a young boy and his pregnant mother from a car wreck and, after watching Casey interact with the kid, Brett stared at him longingly. "Jump him already," Brett's partner, Emily Foster (Annie Ilonzeh) said after catching sight of the glance. 

Later in the episode, Chief Boden invited Casey to a double date dinner: "Sounds like I need to find a date," Casey said.

He immediately walked over to the garage, where he watched Brett and Foster pull in and high-five. "Brett, so..." Casey started to say as he walked over to her, but was interrupted by Christopher Hermann (David Eigenberg) and Darren Ritter (Daniel Kyri).

"What did you want to ask me?" Brett asked when Hermann and Ritter's conversation subsided. "Let me get back to you later," Casey said.

But later, he saw Brett hug her ex Kyle Sheffield (Teddy Sears) and assumed they were back together, so he did not ultimately ask her to the dinner.

Casey and Brett Reunited

Brett ultimately did end up pursuing a new relationship with Sheffield at the end of Season 7 and the beginning of Season 8—even temporarily leaving Chicago to live with him in Indiana. The couple broke up shortly after, and Brett returned to Firehouse 51, much to the team's excitement. 

Upon seeing her, Casey gave Brett a hug and said "51 just hasn't been the same without you." The two exchanged a short, loaded glance, a nod at their near-miss moment from the Season 7 finale (Episode 22 "I'm Not Leaving You.") 

Foster Teased Brett About Casey

In Season 8, Episode 9 ("Best Friend Magic") Dawson made an unannounced appearance and caused a rift in the escalating closeness between Brett and Casey.

Brett ran into Casey in the firehouse shortly after his reunion dance with Dawson, and asked how it went. Casey said it went well, to which Brett responded, "That's so, so good to hear." Always hyper-aware of her partner's micro-expressions, Foster mocked Brett, "So, SO good to hear", to which Brett replied, "He seems happy. That makes me happy." 

Casey Supported Brett After Her Mother Died

Brett had an eventful end to Season 8 when she reunited with birth mother, Julie, who shortly thereafter announced that she was pregnant again. Julie believed that Casey and Brett were a couple, and doubted Brett when she told her that they were just friends.

Unfortunately, Julie passed away giving birth to Brett's half-sister in Episode 18 ("I'll Cover You"), but Casey was there to hold Brett through the aftermath. 

Grainger Asks Brett About Casey

In Season 9, Brett ended up pursuing Greg Grainger (Jon-Michael Ecker), who was at odds with Casey for multiple reasons. After telling Grainger to not worry so much about Casey's opinion, Brett was forced to define their relationship. 

"You two had something, didn't you?" Grainger asked. "I don't know. It's a long story," Casey replied, flustered. "It was somewhere between something and nothing, but..." Grainger interrupted: "I could tell there was more going on." 

Brett Helped Casey Face Medical Fears

In the middle of Season 9, Casey feared the worst after suffering from headaches and vision difficulties as a result of a work injury. In a triumphant, heartstring-jerking moment, he was cleared for work and told that he was simply suffering from post-concussion symptoms. Brett was by his side the entire time, bringing the two even closer together. 

Casey Stayed Over at Brett's

In the first episode of Season 9 ("Rattle Second City"), Brett and Casey's close relationship became even closer when Casey helped protect her. Brett was held at gunpoint during a rescue at the beginning of the episode and forced to treat one of two criminal brothers. The brother later died, and Brett feared that the man who held the gun to her head would come back for revenge.

She asked Casey to spend the night with her, and the two ended up playing games and laughing the night away. 

Brett tried to give Casey an out, saying "It's getting really late," but Casey interrupted her: "I'm staying, Sylvie," he said while smiling. 

Brett Kissed Casey

In Season 9 Episode 2 ("That Kind of Heat"), Brett's ambulance was run off of a bridge by the brother she feared would hurt her. Casey and Truck 81 ran to the rescue (with Casey jumping out of the vehicle to get to Brett faster), opening up another chance for Casey to take care of Brett. In the aftermath, Brett told Casey, "It's always been you." 

Later in the episode, as tensions between the two escalated, Casey showed up at Brett's house to ask why she was avoiding him. "So I wouldn't end up doing this," Brett said, kissing him. 

Casey Moved to Oregon

Fans of Chicago Fire know that the inevitable downfall of Brett and Casey's romance began when Casey decided to move to Oregon to be a stand-in parent for his late teammate Andy Darden's (Corey Sorenson) two sons. In their heartfelt goodbye in the show's 200th episode (Season 10 Episode 5, "Two Hundred"), Casey told Brett: "But you and me, I want to keep being you and me."

Casey and Brett Reunited at a Wedding

Kara Killmer As Sylvie Brett and Jesse Spencer As Casey dancing together

In a heartfelt reunion between the couple at the wedding of Casey's partner, Kelly Severide (Taylor Kinney), Casey and Brett acknowledged the plight of being in a long-distance relationship. They danced together during the wedding reception, and talked about if it was still worth staying together. 

“How much longer can we keep this up?” Brett asked. Casey replied, “I don’t know, but we’re together tonight.”  

Casey and Brett Decided to Break Up

The current state of Brettsey isn't exactly their happy ending. After long-distance visits, love letters, and phone calls, Brett broke up with Casey over the phone in the show's Season 11 Episode 1 ("Hold On Tight"). "Our stars just didn't align," she told him. 

Casey Proposes to Brett

Brett’s personal life was a focal point in the Season 11 finale of Chicago Fire. After she decides she wants to adopt a baby, her current boyfriend, Dylan (Christopher Allen), breaks up with her, saying they’re in two different places. Meanwhile, Casey — who’s in Chicago helping out on a case — catches wind of this. Realizing he isn't over Brett (and never really was to begin with), he shows up to her house at the end of the episode and proposes. He wants the two of them, Darden’'s sons, and Brett’s soon-to-be little girl to become a family. "Sylvie Brett, we were meant to be," he says. "Will you make me and the three kids the luckiest family in the world? Marry me."  We won’t find out Brett’s answer until the Season 12 premiere in fall 2023.