Jon and Kate are also parents to twin daughters, Cara and Mady, 22.
Jon Gosselin is celebrating a milestone moment in his children's lives.
The former reality star took to Instagram Wednesday to wish his and ex-wife Kate Gosselin's sextuplets -- Hannah, Leah, Alexis, Joel, Aaden and Collin -- a happy 19th birthday.
Sharing a photo of the kids as little ones, Jon wrote, "HAPPY 19th BIRTHDAY to all my Kids!! I love you all so much!!"
Jon also shared more shots of the sextuplets on his Instagram Story, including another look at the bunch as toddlers and another story post echoing that same happy birthday message.
Jon and Kate are also parents to twin daughters, Cara and Mady, 22.
Jon caught flack in the comments, however, with fans pointing out that the sextuplets are not "all" his kids, making reference to Cara and Mady.
ET recently spoke with Mady's younger brother, Collin, 18, who has been living with his dad, Jon, and his fellow sextuplet, Hannah. According to Collin, he has not spoken to their other siblings in about six years.
"I haven't reached out to them, they haven't reached out to me," he said. "I want to respect their space and their time and respect how they feel about everything, so I'm kind of just waiting for the day that they reach out. I don't want to reach out. I don't want to invade their space. I'd rather just let them do it on their own terms."
While they have not been in contact, Collin had only kind words for his brothers and sisters. "I love my siblings. I would be willing to put my parents aside and I have. In my eyes, it's me and my siblings. I love them to death," Collin said through tears. "I love them very much. How I see it is, without parents involved, it's just me and them. I really hope that one day when I have kids that my kids will know their aunt and uncles."
"I hope they're doing well," he added. "I hope they're living the lives that they want and that they're happy."
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