Surprise! Brandon Jenner Marries Pregnant Fiancée Cayley Stoker in Courthouse Wedding

Steve Helling

Brandon Jenner is a married man!

“We wed at the Santa Barbara Courthouse on Jan. 21 with my daughter Eva and Cayley’s grandmother, Joan, as our witness,” Jenner, 38, tells PEOPLE of his wedding day.

While wishing a pregnant Cayley Stoker a “Happy Birthday” on Sunday, the reality star revealed that the couple had tied the knot.

“Happy Birthday to my beautiful wife, Cayley,” he began a lengthy Instagram post on Sunday. “I have discovered a whole new level of happiness because of you.”

RELATED: These Celebrity Couples Ditched a Big Wedding (at Least at First …) for an Intimate Courthouse or City Hall Ceremony

Jenner continued, “You are smart, kind, funny, driven, caring and super pregnant at the moment with our twin babies!! 🙌🏼❤️❤️🙌🏼 I will forever cherish what we have together and am so looking forward to celebrating every one of your birthdays with you from here on out. 😁👌 Eva, Onyx and I are so unbelievably lucky to have you in our lives. 🍀 Thank you a trillion times over for loving me the way you do. ❤️🙏🏼❤️.”

Alongside the note, the father-to-be shared what looks to be one of the couple’s wedding photos, with the couple embracing and the expectant mother wearing a white dress.

RELATED: Brandon Jenner and Pregnant Girlfriend Cayley Stoker Are Engaged

Jenner also included several other outtakes of their life together, including a sweet screenshot of a FaceTime call, and photos from trips they’ve taken together.

On Saturday, he shared a heartwarming video on Instagram with the caption, “It’s official,” along with engagement ring and heart emojis.

News of the Jenner and Stoker’s marriage comes as they are preparing for their babies on the way.

RELATED: Brandon Jenner Says He Feels Like the ‘Luckiest Man Alive’ at Pregnant Girlfriend’s Baby Shower

Brandon Jenner and Cayley Stoker | Courtesy Brandon Jenner

In August, the couple announced that they are expecting twins. “We’re madly in love and we are very excited about this!” Jenner told PEOPLE at the time.

Earlier this month, the parents-to-be recently celebrated their pregnancy with friends and family at Stoker’s baby shower in Malibu.

“👶👶🚿 I feel like the luckiest man alive 🙏❤️,” Jenner captioned his social media post from the event, which featured also Linda Thompson, who shares Brandon with ex Caitlyn Jenner, and Caitlyn’s close friend and business partner Sophia Hutchins.