There is no such thing as old or young soul. A soul is timeless, soul has no date of creation it had always been here at the part of the whole. This is MK stuff to make some people (especially in esoteric areas) feel themselves "elected".

You are the product of the potential given by your DNA and your upbringing/past history. Maybe "your" soul had more experience in refining what it wanted to be, that's all.

A so called old soul doing nothing of this potential in this life and waiting for everything as given may end up as a monkey next life for wasting the chance.