During the 2023 holiday season, Hilary Duff shared big news: She is expecting her fourth child and third with husband Matthew Koma.

But who is her longtime leading man? Matthew Bair—better known by his stage name Matthew Koma—has been by her side since 2017. They already have two daughters together, Banks and Mae, in addition to Duff’s son Luca whom she co-parents with her ex-husband Mike Comrie.

Koma’s own background and repertoire of projects is enough to impress in his own right, though. Below, get to know Duff’s partner and their history.

He’s the lead singer of a band.

Koma heads up the four-piece indie pop group Winnetka Bowling League. The band, which includes Koma’s brother Kris Mazzarisi on the drums, formed in 2018 and signed to major label RCA shortly thereafter. Their second EP, Congratulations, was released during the pandemic and received glowing praise from Duff.

Before starting Winnetka Bowling League, Koma released his own music as a solo artist. He was first discovered by music business mogul Jimmy Iovine, co-founder of Interscope Records and Beats Electronics. Koma went on to tour with Ellie Goulding, LMFAO and Owl City, and played festivals like Coachella and Ultra.

He’s written songs for Britney Spears, Demi Lovato, and Zedd.

Outside of his own projects, Koma has written a number of songs for other successful artists. His big break came from working alongside EDM artist Zedd. Koma co-wrote and sang on Zedd’s hit song “Spectrum” and co-wrote “Clarity,” which won a Grammy for best dance record in 2012. Despite their success, the relationship between the two turned sour. Seven years after the release of “Clarity,” Koma made headlines for calling Zedd “toxic” and “self-serving” in a lengthy Instagram post.

Drama aside, Koma has credited the collaboration for creating other musical opportunities, like songwriting for Tiësto, Kelly Clarkson, Shania Twain, and 5 Seconds of Summer. In the past year, Koma has co-written songs for two pop icons: Britney Spears and Demi Lovato. Spears’ “Swimming In The Stars” was the fourth single to be added to the deluxe version of her 2016 album Glory. “Easy,” featuring Noah Cyrus, is the 13th track from Lovato’s album Dancing With The Devil… The Art of Starting Over, which recounts the singer’s 2018 relapse and overdose. Following their collaboration, Lovato regularly appeared in Koma’s Instagram comments, proving their friendship went far beyond the recording studio.

He dated Carly Rae Jepson for a few years.

The “Call Me Maybe” singer told E! News that she met Koma in 2012 while recording her song “The Kiss.”

“Believe it or not we’re, like, super professional when we get into the studio together,” Jepson said. According to a 2013 interview with People, the couple made an effort to see each other at least once a week despite tours and busy schedules. For the most part, Koma and Jepson kept their romance out of the limelight until their split in 2015.

Koma and Duff met while working together on her 2015 album.

The couple met back in 2015 when Duff enlisted Koma to help with her fifth studio album Breathe In. Breathe Out. At the time, Duff was separated from her now ex-husband, former hockey player Mike Comrie. Koma and Duff made their relationship red carpet official in 2017 at a pre-SAG Awards party. The pair was in an on-again-off-again relationship for a few years before settling down together.

“We knew we just had to be together because we tried a bunch of times to be apart, and that didn’t work out for either one of us,” Duff told People in a 2021 interview. “And then the third time was the charm.”

The couple share two daughters together.

After reuniting, Koma and Duff decided to have a child together. Duff gave birth to their daughter Banks Violet Bair on Oct. 25, 2018. Two years later, Duff announced in an Instagram post that she was pregnant again, writing, “We are growing!!! Mostly me…” alongside a boomerang of Koma rubbing her belly. Their second daughter, Mae James Bair, was born on March 24, 2021 via an at-home water birth.

As for Luca, Duff’s 11-year-old son from her previous marriage, he and Koma formed an instant bond when meeting. “Matt was going trick-or-treating with us, so we showed up to Matt’s house and he was dressed as a full-blown Donatello Ninja Turtle and Luca was like, ‘You’re gonna be my best friend,’” Duff told People in May 2021.

Koma chimed in, saying, “He’s such a great kid, and he’s so sensitive that it was really easy to connect with him.”

Koma and Duff have both raved over one another’s parenting skills, penning thoughtful tributes to one another on Father’s and Mother’s Day.

They announced they were expecting their third child together in December 2023.

Duff shared a pregnancy announcement post featuring their holiday card. “Surprise Surprise!” she captioned it.

They wed at their Los Angeles home in December 2019.

In between the births of their two daughters, Koma and Duff tied the knot. Koma proposed in May 2019 at a park near their New York City apartment. Seven months later, the two married in an intimate ceremony days before Christmas. The wedding, planned by celebrity wedding planner Yifat Oren, was held in the front yard of their Southern California home. “Our wedding isn’t over-the-top ‘wedding-y’—it’s more understated and for me, that’s more powerful,” Duff told Vogue. Luca accompanied Koma to the altar, and Duff held their daughter Banks as she made her way down the aisle in a Jenny Packham gown with cape-like sleeves and an open back.

Koma and Duff sang together on a love song.

In 2020, Koma and Duff were featured on RAC’s remix and cover of Third Eye Blind’s “Never Let You Go.” The song, released just two days before Valentine’s Day, takes on a more bubble-gum sound than the original thanks to the married couple’s harmonies. Besides this cover—and a second cover of Fleetwood Mac’s “Little Lies” for her TV series, Younger—Duff’s last musical endeavor was her 2015 album, Breathe In. Breathe Out., the project responsible for Duff and Koma’s introduction.

The then-newlyweds quarantined together as a family.

Three months into marriage, the two were spending every moment together in quarantine. Duff told Forbes that the family got creative with obstacle races, toys and board games to keep their children entertained during the pandemic. She also joked in her November 2020 cover interview with Cosmopolitan UK that Koma was a quarantine expert: “He’s like, ‘We have everything we need, what’s bad about this?’ I’m a homebody too, but I do need to go out with my girlfriends once in a while,” Duff said. Koma all but confirmed this sentiment in a 2017 video series with Billboard. “My guilty pleasure is cancelling plans,” he confessed. “I hate plans. When something gets cancelled, I’m secretly so happy.”

Koma and Duff are not shy on Instagram.

Koma is a romantic. Take it from his 2015 song, “I’m so fuckin romantic”—or from the numerous declarations of love that he’s posted online. The husband-and-wife duo don’t mind letting their fans in on their romance. Anniversaries, Valentine’s Day, sweet gifts and polaroid photos posted to the stars’ social media accounts give followers an intimate look at their relationship and family life.

For Koma’s 36th birthday in June 2023, in one recent example, Duff shared an adoring tribute, writing, “Matthew- here are some of my favorite pictures reminding me of all the happiness and exhaustion we plow through together. This family loves you so much – I love you so much – Happy 36 my love, I’m right behind you 💕 thanks for making me laugh like no other and making sure to be everywhere all at once for us ♥️. @matthewkoma my forever leg tangle… just 1 more?🫠🥱🤗 Forgive me for my day late post …( I’ve really taken the pressure off posting lately and it feels so good☺️)”