On Monday, the singer-songwriter, 33, debuted a new tattoo of the Lizzie McGuire alum's first name inked in cursive script, by sharing a hilarious photo of his bare backside on Instagram. Koma kept the snap PG by adding peach emoji stickers, but he didn't hold back in the caption.
"Good luck winning a fight with your wife when her name’s tattooed on your butt cheek. #squats #gainz #laseraway," the star, who shares 22-month-old daughter Banks Violet with Duff, wrote alongside the belfie (butt selfie).
But what did Duff think? She applauded her hubby by commenting, "Finest tiniest booty around #youstucknowboy."
This isn't the first time Koma got ink in honor of his family. In November he shared a photo of his new arm tattoo featuring his step-son Luca, 8, and daughter Banks' hands sweetly clasped together.
“Luca (7) and Banks (1) holding hands just after her 1st birthday. Thank you @curtmontgomerytattoos for engraving my kids,” Koma captioned the post at the time, tagging both tattoo artist Curt Montgomery and Duff.
The couple tied the knot on Dec. 21, 2019 in a “small and low-key” ceremony at their home in Los Angeles, PEOPLE confirmed at the time.
Hilary Duff/Instagram Hilary Duff, Matthew Koma and daughter Banks
The wedding came seven months after Duff and Koma announced their engagement in May 2019.
Duff was previously married to former hockey player Mike Comrie from 2010 to 2016. The couple share son Luca Cruz.
In June 2018, Duff and Koma announced they were expecting their first child together. Four months later, in October, Duff and Koma welcomed daughter Banks Violet Bair.
Emma McIntyre/Getty Hilary Duff and Matthew Koma
"Banks Violet Bair this little bit has fully stolen our hearts! She joined our world at home on Thursday afternoon and is absolute magic,” Duff wrote along with a portrait of herself cradling their baby girl with Koma.
The proud new dad also shared the exciting news, writing, “Banks Violet Bair /// 10.25.18 /// We welcome a beautiful daughter, little sister, and best friend for life. Could not possibly be more grateful for our growing family and for the ? who makes it all possible. Cloud ten.”
Seven months after the birth of their first child, Duff announced on Instagram that Koma had proposed to her, showing off her ring in a sweet selfie of the couple.
“He asked me to be his wife,” she captioned the post. Koma posted the same photos, writing: “I asked my best friend to marry me… @hilaryduff.”
Duff and Koma's surprise wedding was confirmed on Dec. 22, with a source telling PEOPLE, “The wedding was at her house. It was small and low-key. Only family and close friends.”
“The ceremony started at sunset and they got married inside the house. When the ceremony was over, guests cheered. The reception was in a white tent in the backyard,” the source added. “Her sister Haylie was very involved in the wedding prep too. Hilary and Haylie are very close.”