In Hinduism, it would be considered remnants of the last lifetime, or former lifetimes. The soul has yet to build its new physical body, its new subconscious, its new ego, its new personality. As all these things develop, the old is slowly forgotten about. The soul naturally just wants one of these new 'machines to work out more karma in' at a time, but in the transition period, its sort of like having two.
Same principle as when in a single lifetime, the embodied soul moves houses or buys a new car. For awhile the old house is still in the subconscious, but over a few years its effects and memories dissipate.
But age 11 is a bit old for this sort of stuff. The new 'person' is quite developed by then. I see this type of questioning more as a psychological development, entering what Piaget termed 'formal thought'.