Orphans are a very popular archetype. Just a few that come to mind are Harry Potter, Annie, Oliver, Luke Skywalker, Simba, Bruce Wayne, Superman, Zeus, Peter Parker...
So what is it about a kid who has lost his/her parents that makes them so appealing? Once a child becomes an orphan, something clicks and the drive to be self-reliant, to go out and make their own way. We see characters often who don't to accept the quest before them because of family connections, but if all those connections are taken away, the launch into the quest just makes sense.
Another element that is appealing about an orphan character is they can be molded, especially if they were orphaned young. No longer do they have to follow in the path of their parents. The mentor generally can see the potential, foretelling, destiny, legend, what have you in the child and doesn't have to persuade parents of the truth.
But the character who has lost parents is often looking for that connection, which makes the battle over them between the good and bad start before the orphan even knows what is going on. They are like molding clay, completely open to become what the mentor would have them be.
Most of the time, an orphan will return to their home - either what was their home or what they came to know as home with the intent to improve the place they came from or say their final goodbyes, with the intent to never return again. It is either to realize they have risen above what caused them so much pain or with the commitment to make sure no one else from there has to suffer the sorrow they experienced.
Have you felt the draw to write an orphan story? Who is your favorite orphan character literature/movies?