Yet, Rob encounters one surprise during the show 's third episode, “What Fucking Lily Girl:” the age of her dreamy musician crush, Liam (Thomas Doherty). Liam, 29-year-old Rob learns to her mortification, is fresh out of high school and roughly 19 years old. It’s the kind of jarring plot turn that will likely have fans wondering just how old the person playing Liam, Scottish actor Thomas Doherty, actually is.