It is an interesting aspect, Daniel.
I would like to focus on one case study to save time. If you can recommend one, please do.
As a general comment, it is possible for something like this to happen. But the following must hold:
1. A given gandhabba can be in only one body at a given time.
2. It is possible for a gandhabba to come out of a womb, and for another gandhabba to take possession of that zygote in the womb.