The Duncans a European-American family in Colorado is adjusting to the surprise birth of their fourth child, Charlie. When parents Amy and Bob return to work they put their latest addition in the care of her three older siblings, PJ, Teddy, and Gabe. Teens PJ and Teddy and tween brother Gabe are typical kids -- that is, until their mother has another baby. The arrival of their new sister completely upends the entire household. When their mother heads back to work after Charlie's birth, it's up to the kids and their dad to keep the home fires burning -- and to keep Charlie out of trouble as she learns to sit up, crawl, walk and run. Teddy, as the older sister, makes a personalized video diary for Charlie, in each episode adding a nugget of wisdom for her baby sibling.