By Elizabeth Leonard
February 23, 2018 at 02:22 PM EST
Allen Berezovsky/Getty Images

James Van Der Beek is about to be back on newborn diaper duty.

The What Would Diplo Do? showrunner and star — who is currently shooting for Ryan Murphy’s new FX series, Pose — is going to be a dad for the fifth time. Wife Kimberly is pregnant, he announced on Instagram Friday, sharing a photo of their four children placing their hands on their mama’s bare belly.

“Thrilled beyond belief to announce that we are once again adding to our family,” Van Der Beek captioned the adorable shot.

“And I say ‘beyond belief’ because some people are probably wondering if we’re out of our minds,” he added. “Which we might very well be … but I couldn’t be more excited. Or grateful. Or in awe of @vanderkimberly.

The new baby will join big brother and sisters Emilia, 23 months, Annabel Leah, 4, Joshua, 6 next month, and Olivia, 7.

Van Der Beek, 40, and Kimberly, 35, tied the knot in August 2012, welcoming Olivia the next month. The “small, spiritual ceremony” took place in Tel Aviv, Israel, where the couple met in 2010.

The Don’t Trust the B—- in Apartment 23 alum opened up to PEOPLE this past August about his life as a father of four — including his household’s favorite holiday.

“I’ve got kids who love Halloween so much they celebrate it throughout the year,” he said. “My son, a month ago was like, ‘Daddy, fog machine, please?’ So we got out the fog machine, we got out the Halloween decorations, they wanted it spooky so we had spider webs up, they just love Halloween.”

Van Der Beek further explained that becoming a father changed his perspective on the work he chooses to do.

“The second I had kids, they immediately became my priority and everything I did existed to support the life that was all about them in a good way,” he said.

“What’s been fun about the work that I’ve been doing is that it’s so playful and kids bring out that playful side of you, so I think that’s gone hand in hand.”