"Happy 39th birthday to one half of the iconic Olsen twins, Mary-Kate! 🎉 It's hard to believe that Jun 13th marks another year of the talented fashion designer and actress dominating the industry. But let's be real, age is just a number when you always look fierce and fabulous like you do. Here's to twinning with your twin Ashley for many more years to come! 🎂 #StillNotConvincedYou'reNotSecretlyOnePerson #ForeverFanOfTheOlsens"