Andi Mack (2017 ) "Andi Mack" is a contemporary, coming-of-age story about a girl who's trying to determine where she fits in and the many amazing ways she can live her life. When her free-spirited older sister Bex returns home with a revelation that changes everything, it sends Andi on an uncharted course of self-discovery. Life goes from routine to a roller-coaster ride overnight for artistic teenager Andi Mack. It all happens on the eve of her 13th birthday when free-spirited older sister Bex -- who has been traveling around the world -- returns home to make a revelation, which changes everything for the Mack family. It turns out that Bex isn't Andi's sister -- she is her mother -- and Celia, who Andi thought was her mom, is actually her grandmother. Learning this family secret sends Andi on an uncharted course of self-discovery. She's not alone on her journey, as best friends Cyrus and Buffy are also trying to figure out their places in the world.