Sophie Turner turned 21 years old on Tuesday, and her Game of Thrones costar and real-life bestie Maisie Williams wasted no time in wishing her a happy birthday. Maisie posted an adorable throwback photo of the two on Twitter, writing, "Happy 21st Birthday @SophieT Forever looking up to you, in more ways than one ❤️." In the snap, a tiny Maisie stares up at Sophie during what looks like a bookstore appearance. Of course, this isn't the first time the two have put their friendship on display. Sophie and Maisie, who were 13 and 12 respectively when Game of Thrones started, have shared a ton of adorable moments together over the years. Most recently, Sophie had her friend's back when she adjusted Maisie's dress on the red carpet at the Golden Globe Awards in January.