James Van Der Beek Celebrates Oldest Daughter Olivia's 13th Birthday: 'Humbled and Honored to Be Your Dad'

The actor reflected on his admiration for his daughter as she steps into her teen years

James Van Der Beek officially has a teenager among his brood.

The Dawson's Creek alum, 46, posted photos on Instagram Monday of daughter Olivia as he reflected on the oldest of his six kids turning 13.

"Cannot BELIEVE it’s been 13 years… It feels like yesterday I was staring into your little bassinet in the hospital, beyond exhausted, but unable to close my eyes and stop looking at you - and realizing I’d never be able to communicate just how cool it was to have a little you," he wrote.

"You expanded my heart and my soul’s capacity the second you came out in ways I could’ve never imagined. You taught me what love was in an instant. And you’ve led the way ever since."

The proud dad continued, "Thank you for being you. For your kindness that somehow surpasses even your coolness, for your drive, your creativity, your A+ stink-eye and your smart-ass sense of humor. And for still thinking I’m funny. I love you for everything you are, and everything I see you becoming."

"Humbled and honored to be your dad. And I’ll always be your #1 fan," he concluded. "Happy birthday, my TEENAGER 😳❤️."

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Related: James Van Der Beek Uses His Daughter to Clean RV at a 'Pit Stop' During Family Vacation

Van Der Beek shares his six children — Jeremiah, 21 months, Gwendolyn, 5, Emilia, 7, Annabel, 9, Joshua, 11, and Olivia — with his wife Kimberly.

In May, the actor spoke to PEOPLE about having a "humbling" life with his six kids. While discussing his family's commitment to an hour of uninterrupted play each day, Van Der Beek said that getting all six of his kids outside "feels like the antidote to getting on a screen."

Talking about spending time with his kids in and around their Texas home, Van Der Beek told PEOPLE, "We're lucky enough to have the space to kick a ball around."

"Even when we were in L.A., trees were our best babysitter," he laughed. "But the fact we can now go outside, and they can watch the seasons change, it's ideal."

Van Der Beek knows that time together is also important for developing the relationships between his kids.

"I think the biggest delight I find is how they interact with each other. They all take care of each other. Sometimes they step in to help solve problems of their own volition," he said. "And the moment I see them looking after their baby brother, I really feel like, 'Oh man, for whatever I've done wrong, I'm doing something right here.' "

Of parenting, he later added, "There are so few general maxims that apply to every kid when you're raising them. I mean, you got the six same ingredients, same recipe, raised in the same house, and they're all different."

"It's just humbling. When you think you've got it down, you get one that throws a curveball at you. And it's regulating our own emotions when things do get hectic and chaos ensues, which is inevitable at times."

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