Jim Gaffigan Says His Five Children Still 'Constantly Surprise' Him 'In Different Ways'

Though Jim Gaffigan has been a parent for nearly two decades, the 55-year-old father of five says his kids still "constantly surprise" him.

The stand-up comedian, who shares his children with wife Jeannie Gaffigan, tells PEOPLE that their kids — Marre, 17; Jack, 16; Katie, 12; Michael 10; and Patrick, 9 — often "surprise me in different ways."

In fact, Gaffigan says he is "constantly surprised" by how funny his son Jack is. He even suggested that the 16-year-old "truly is one of the funniest people" he knows.

"I've lived with him for 16 years. I've seen him be funny, consistently quickly. He doesn't struggle with it," Gaffigan tells PEOPLE of his son, who is hosting shows on his father's cross-country comedy tour.

Gaffigan adds that his son recently performed at an arena in front of 7,000 people, which he says is "the biggest venue" of his son's young career.

"I didn't assume, I didn't pressure him to wanting to pursue stand up," the comedian tells PEOPLE. "I mean, he's also 16. He wants to do it now. But, when he's 18, he might be like, 'I'm never doing it.' "

Gaffigan says he is also "constantly surprised" by how much he learns from both his eldest and youngest children. Gaffigan tells PEOPLE that his youngest, Patrick, "surprises" him with the "insane" level of knowledge he has on "scientific things" while the oldest, Marre, is a "social justice warrior"

"[Marre] educates me on things without a sense of judgment," he tells PEOPLE, "which is amazing."

Meanwhile, Gaffigan describes his 12-year-old Katie as "a true rebel," and says son Michael is "way more athletic than anyone in our family."

Gaffigan first shared his thoughts on life as a parent of growing children on the latest episode of CBS Sunday Morning. During the segment, the jokester admitted to being wrong about how unpleasant raising kids can be.

"I'd like to apologize," Gaffigan said in the piece. "I was wrong. Dead wrong. Having five young children was a beautiful thing. I know that now because I presently have five not-young children," he added before quipping that his life "is absolutely horrible" now.

"I remember thinking, 'If we could just get these kids out of diapers, our lives will be so easy," he continued with a chuckle, calling himself "naïve" and "arrogant" for doing so. "I didn't know back then when a stranger would see me with my young kids and volunteer, 'You're going to miss this!' I thought they were weirdos with no boundaries. I didn't realize that stranger was bestowing a warning upon me."

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One thing Gaffigan "didn't really delve into" in the piece is the stress that comes with parenting kids through their preteen and teenage years, which he tells PEOPLE can be even more stressful than some might realize.

"We always hear like, 'Oh a baby, it's such hard work [having a baby]. You're not getting any sleep.' But the reality is, the stress associated with a baby is nothing compared to the stress of having even a preteen," he explains. "They're being attacked by hormones. You're losing any authority or influence you have over them and they're finding their way for independence and it's terrifying."

"A baby bumping their head on a coffee table is terrifying. But, you can keep an eye on it," Gaffigan continues. "But a teenager trying to figure out judgment on dealing with mean people, you're not there."