Happy 23rd birthday, Anastasia Karanikolaou! Kylie Jennertook to Instagram on Tuesday to celebrate her best friend's birthday, and alongside a series of photos of the duo, she described Stassie as the "rarest of all time" and "truly a gift to this world." Even more sweet, Kylie called Stassie "the best aunty to my babygirl," Stormi Webster. "i can't believe we are celebrating your 23rd birthday," Kylie continued.