Whats got me wondering is when a loved one dies, you expect to see that person on the other side when you die.

But what if when you get to the other side, your loved one has already been reincarnated. Do you miss seeing your loved one??

I am thinking that the OP's suggestion of an oversoul could work. Perhaps the oversoul stays on the other side and the soul that comes here to live and gain experience is just a part of that soul. Hence the oversoul always stays on the other side and advances depending on how the earth soul did while it was here.