The 38-year-old American actress and her musician husband Josh Kelley, 36, welcomed their third child together on December 20 of last year.
The little arrival - a happy and healthy boy, who the couple have named Joshua Bishop Kelley Jr - joins big sisters Adalaide, four, and Naleigh, eight.
Katherine, who is perhaps best known for her role as Izzie Stevens on Grey's Anatomy, took to Instagram to share a darling photo of little Josh snuggled safely between his proud parents.
She captioned the adorable snap, “@joshbkelley and I are beyond thrilled to finally share the arrival of our little man Joshua Bishop Kelley Jr born December 20th, weighing in at 7 pounds 15 ounces. We are all happy, healthy and beyond grateful!”
The photo, which is the first of little Josh to be released publically, comes as part of Katherine’s candid new cover story with People magazine.
Speaking with People at her Utah ranch, Katherine revealed that baby Josh’s birth wasn’t exactly planned.
She said, “It was a surprise! I knew I wanted to expand our family, I knew I wanted to have more children.”
Before adding, “I’ll be totally honest, my first reaction was ‘Oh s—.’ But now we have a new normal, and I have to give myself a break in order to get used to it.”
Another highlight from the interview was the sweet way Katherine chose to explain Josh’s impending arrival to her two daughters.
Katherine recalled that she waited until she was 12 weeks along before sharing the exciting news with her adorable daughters - but, they were among the first to know about the baby, only second to the Life As We Know It actresses mum, Nancy.
She said, “I was so relieved to get to share it.”
“[The news] was a little confusing for the girls because they’d be like, ‘I grew in your tummy?’ And I had to explain, ‘Well, you didn’t actually grow in my tummy, but your dad and I are your parents.’”
Katherine and Josh decided upon adoption for their first two children as adoption had always been a part of Katherine’s life. Her older sister, Meg, was adopted from South Korea - daughter Naleigh’s native country.
The couple adopted little Adalaide from a woman in Louisiana.
In the same interview with People, Katherine explained how she broached the subject of adoption with her daughters. She said, “My sister had a book growing up that we all read and we all loved called Why Was I Adopted?”
“That was the first gift she gave Naleigh when Naleigh came into our lives.”
The Knocked Up actress added that she’d also found a touching poem about adoption useful.
Recalling the words of the poem, she said, “You didn’t grow under my heart, but in it.”
She added, “My mother used to say this too: ‘It doesn’t matter how they come into your life,’ ‘The moment they put that child into your arms — whether you just [gave birth] or whether they just arrived from Korea — they’re yours.’’
But Katherine admits that the youngest members of her brood are yet to fully understand their unique family makeup.
She said, “At the ages they are now, I don’t even think they much acknowledge how different we all look. I don’t think that even factors into their consciousness at this point. It will as they get older, they’ll be like, ‘Wait a minute, we all look really different, and what does that mean for me?’”
Until then, Katherine explained that she and her hubby are there to support them “as parents do.”
“It’s all about open communication and helping them access whatever they need to feel absolutely 100 percent secure in who they are.”
“Whether that’s about their history, their heritage, their race, their memories … we’re there.”
For the moment, the young family is taking the time to enjoy their newest addition with Katherine admitting that they're all "really obsessed with him!”
She added, “With a newborn, you’re forced to be still … and you have this beautiful reason to do that.”
But Katherine did hint that despite being busier than she’s ever been, Josh’s arrival hasn’t deterred her from expanding the family’s ever-growing brood one day soon.
She said, “I’d get pregnant again, and I still am very inspired by adoption. I also have been thinking a lot about fostering. It’s all up in the air” before adding, “And I’m okay with that!”
Last year, the now-mother-of-three confirmed that she and Josh were expecting via a picture of her sonogram on Instagram.
The proud parents shared a statement after they discovered they were expecting a new addition to their family.
“The Kelley clan is thrilled to announce that we are expecting a third addition to our family,” the couple penned in a letter to People.
“Naleigh and Adalaide [pictured below] could not be more excited to welcome their new sibling into the fold, and Josh and I are overflowing with joy and gratitude.”
“This is an incredibly exciting time for us filled with hope, anticipation and hormones. Well, only I’m filled with hormones, but everyone in the family gets to enjoy them,” the star joked.
“We couldn’t be more excited to be able to finally share this news with our fans, and are looking forward to continuing to share the journey with you all.”
Congratulations again to the happy family!
This story originally appeared on Woman's Day Australia