A representative for the 39-year-old star confirmed the baby's arrival to PEOPLE. The rep, however, has yet to offer more details of the newborn like their name and gender.
The news came after Jonah was noticeably absent from sister Beanie Feldstein's wedding. He and his rumored fiancee didn't appear in any photos from Beanie's wedding to producer Bonnie Chance, which took place on May 20.
Johan and Liv, who is the co-founder of online vintage site Chasseresse with her big sister Raychel Roberts, were first publicly photographed together in August 2022. It, however, is unknown how long they have been together as the actor has been keeping his personal life private.
Liv then sparked engagement and pregnancy rumors in March of this year. At that time, she was spotted rocking a large diamond ring on that finger during an outing.
Liv, who was shopping at The RealReal and Burro in Santa Monica, not far from Jonah's $6.7M three-bedroom Southern Colonial home, also sported what seems to be a noticeable baby bump during the solo trip. Her burgeoning belly was clad in a black knit sweater beneath blue denim overalls, which she paired with comfy green slides.
Liv wasn't accompanied by Jonah during the solo outing. She carried a green bag over her shoulder and held a The RealReal shopping bag before heading to a parked car. She also stopped by for a coffee run that day.
Before dating Liv, Jonah was in a romantic relationship with surfer Sarah Brady from 2021. They went Instagram official in September of that year. In February 2022, the "You People" star and producer responded to rumors that they got engaged.