Kate and Jon Gosselin’s kids are all grown up! The matriarch, 49, took to Instagram on Sunday, May 12, to share a rare photo of four of her sextuplets with her ex-husband, 47, to celebrate their 20th birthdays on Friday, May 10. However, Collin and Hannah were noticeably absent due to the family rift. “No more teenagers in this house!” Kate wrote alongside a shot of Alexis, Aaden, Leah and Joel smiling while gathered around a chocolate cake adorned with a candy version of a giant pickle and red jalapeños. “Happy 20th birthday, my forever babies! I love you! Who feels old? I know I do! #20years…