They're all grown up! Kate Gosselin recently wished her twin daughters — Cara and Mady — a happy 17th birthday, and couldn't help but gush about how old they've gotten on social media.

"And then you blink, and they TURN SEVENTEEN!! Happy birthday to my girls!" she wrote on Instagram. "My heart hurts because you're almost adults and will soon leave for college, yet it smiles because I am seeing who you've become: brilliant, beautiful, kind, caring, logical, responsible, empathetic, honest, amazing individuals! I love you both SO VERY MUCH! Let's have a wonderful day together celebrating Y❤️U!"

And her fans were quick to comment on the photo of the girls. One fan wrote, "Happy Birthday to you both. Such a magical age. You've had the best Mom ever…. that's why you are who you are. Great job Kate!!" While another added, "This is how old they were when I started watching. How does time go so fast?" We feel the same way — and can't believe those little girls are teenagers already!

It seems like Kate has a great relationship with her kids, although she did admit earlier this year that she can't imagine the day when all her kids are out of the house. “It’s official: all teenagers. And it’s the day I feared since the day they were born. When the little kids are in college, and my house is empty, I actually can’t even fathom it," she said. "I’ll be the crazy cat lady… except with dogs. I’ve learned not to have any predictions about the next 10 years, because I certainly never thought I’d have wound up here 10 years ago! Given all the drama of our lives, doing a reality show honestly feels like the smallest issue we’ve ever had to deal with.”

Click through the gallery below to see all the kids then vs. now!