So, how does it feel to have six more teenagers?
"It's only been a couple of hours, so we'll see," he tells E! News. "It's going to be interesting!"
That's the understatement of the year!
Kate, meanwhile, shared a collage Wednesday morning via Instagram. "HAPPY 13th BIRTHDAY, my precious Alexis, Hannah, Aaden, Collin, Leah and Joel! At this moment (7:51-7:53 am) 13 years ago, my life and heart were completed with your births! I love you all and NO MATTER WHAT it requires of me, I will ALWAYS be there for you; I'll always be your biggest cheerleader, your role model by example, your shoulder to cry on, the hug and laugh you need, and your mommy and friend! I love you guys! I got six times what I planned on, but I'd NEVER EVER go back!" Kate wrote. "You're the six final pieces of my heart that I never knew I was looking for."
Kate capped her caption with a winking emoji and six red heart emojis, plus three hashtags: "#Turning13Today #HappyBirthdayBabies #ILoveYouToTheMoonAndBack100MillionTimes."
Last month, Jon celebrated a milestone of his own: turning 40. To mark the occasion, the Reading, Penn., resident performed at Dusk Nightclub's "Untamed Male Revue" in Atlantic City. Afterward, he told E! News, "I never said I was going to strip!" Following a decade of "media scrutiny," Jon said, "I wanted to give myself the best 40th birthday present ever. I wanted my family and my friends to be there—and why not have a huge party with an amazing venue?"