Orphans

"You're from Burma, aren't you? Was it nice there? Do you miss your family? (the snake at the zoo gestures to a sign that says "Bred in Captivity.") I see. That's me as well. I never knew my parents, either."

- Harry Potter to a friendly snake.

A recurring theme in fiction concerning heroes is the loss of their parents (usually both), normally at an early age, at least before their 18th birthday. Some orphans get separated from their families and find them. Some never even had parents and are clones born in a laboratory. And sometimes, when the death of both of your parents is bad enough, they are sometimes brought in by abusive guardians.