Dad Jon Gosselin also wished the twins a happy birthday on social media.
Happy birthday, Mady and Cara Gosselin!
Kate and Jon Gosselin's oldest children turned 17 on Sunday, and Kate couldn't help but celebrate with a heartfelt Instagram post.
"And then you blink, and they TURN SEVENTEEN!! Happy birthday to my girls! 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!" Kate captioned a throwback pic of her twins. "I love you both SO VERY MUCH! Let's have a wonderful day together celebrating Y❤️U! #Cara #Mady #SeventeenthBirthday #ILoveYou #ForeverAndAlwaysNoMatterWhat ???????????????."
Jon later added his own Instagram tribute, writing: "Happy 17th Birthday Mady and Cara!!! Love you, Dad."
Kate and Jon, who divorced in 2009 after 10 years of marriage, are also parents to 13-year-old sextuplets: Aaden, Alexis, Hannah, Leah, Collin and Joel.
Kate got emotional while celebrating the sextuplets' 13th birthday on Kate Plus 8 earlier this year. Watch below for more.