I don't think it's typical. But I don't think that means it's abnormal. It sounds like you're really asking if it's pathological . . . like a sign of some emotional disorder. That would depend on if it's associated with a lot of psychic distress. In your case, it sounds like you were dealing with a lot of insecurity. Some children are unusually thoughtful and sensitive, and they think about things that don't preoccupy most children. If the thinking leads a child to a greater sense of security, then I would say the thinking was healthy. If not, then I would say the child is overly burdened with issues that the child cannot resolve healthily. That would spring, I think, from the child not feeling safe. I don't think that's a good position for a child to be in.

What's abnormal, IMO, is not the child's thinking, but the child's living situation that is causing so much stress.