These are family trees from books, movies, and television (and one from real life). In order, reading down the left column and then the right, the missing people (and their originating media) are:
Sheldon (Young Sheldon)
Iroh (Avatar: The Last Airbender)
Bart (The Simpsons)
Sister (The Berenstain Bears)
Aaron (The Mitchells vs. the Machines)
Nigel (The Wild Thornberrys)
Donald (various Disney, notably DuckTales)
Ramona (Beverly Cleary novels)
Edward (British Royal Family)
Nala (The Lion King series)
Thor (Marvel Creative Universe)
Susan (Diary of a Wimpy Kid)
Taking the first letter of each answer in this order gives SIBS AND RENTS, which while often used as a clue for FAM, is the answer to this puzzle in its own right.