The series follows two teenagers, Teddy (Bridgit Mendler) and P.J. Holliday (Jason Dolley), and their 10-year-old brother, Gabe (Bradley Steven Perry), whose parents enlist their help when they return to work after the birth of their fourth child, Charlotte, aka Charlie. With their parents juggling full time careers, the older Holliday siblings pitch in, getting very familiar with baby formula, burps, clothes, and babysitting while navigating typical teenage life. In each episode, Teddy creates a personalized video diary for Charlie. Each video will chronicle Teddy's daily adventures and mishaps for Charlie to use as advice when her big sister is no longer living at home. (Source: Disney)