
The series centers on the Duncan family, who are still adjusting to the surprise birth of their fourth child, Charlotte "Charlie" Duncan (Mia Talerico). When parents Amy (Leigh-Allyn Baker), a nurse, and Bob (Eric Allan Kramer), an exterminator, return to work, they ask their three older children—PJ (Jason Dolley), Teddy (Bridgit Mendler), and Gabe (Bradley Steven Perry)— for help raising their little sister. At the same time, Teddy, PJ, and Gabe try to deal with school and typical social challenges in their life.
The events of each episode become material for a video diary Teddy is making for her younger sister. Teddy hopes the videos will provide useful advice for Charlie after they have both grown up and Teddy has moved out. The series begins when PJ is 17, Teddy is 15, Gabe is 10 and Charlie is nine months old.
- Bridgit Mendler as Teddy Duncan
- Jason Dolley as PJ Duncan
- Bradley Steven Perry as Gabe Duncan
- Leigh-Allyn Baker as Amy Duncan
- Mia Talerico as Charlotte "Charlie" Duncan
- Eric Allan Kramer as Bob Duncan
(Source: Directly from Wikipedia)

