Question: If a soul has already come into a body and then decides to leave, could another soul take its place?

Sri Chinmoy: No, it does not happen that way, except in some mythological Indian stories. Only if the soul changes its plans before it enters into the body can another soul take its place.

From:Sri Chinmoy,Sri Chinmoy answers, part 7, Agni Press, 1996
Sourced from https://srichinmoylibrary.com/sca_7