Features of reincarnations

I've been testing the rebirths and their features in the game a bit, and I want some clarification on why they work this way.
There are many ways to become a ghost in the game, and the weird thing is that you don't have to die to be reborn, you just have to become a ghost and be reborn in a lake. The weird thing is that when you choose to be reborn, the character doesn't die, they stay alive, but with only one character trait. I found this out when I temporarily made my pregnant Sim a ghost through a seance table and, for fun, clicked reborn in a lake in Vranderburg. The pregnant Sim disappeared from the family, gave birth, and with the help of her son I was able to add her back, but it was essentially just a shell, with one character trait, a baby with the same name was on the list of families without a house in the city. The mechanics are weird, not thought out.
I'm also interested in why the Sim only remembers people from his past life, but not from the life before rebirth into that life. I also want to describe another situation that I accidentally generated.
My Sim died with a fully completed soul path. I reborn him as Morgan Fierce's son, then it turned out that he became a vampire and burned in the sun and was reborn as Eliza Pancake's son, but since I really liked Morgan Fierce, I reborn her (using the method indicated earlier) as Bob Pancake's sister. Now I'm confused about what kind of relationship they have. In Social Bunny, I was able to conjure up a romantic relationship for them, they even wanted to go on a date, but the only available romantic actions were to offer a massage. I raised them together, but the relationship has the property "best brothers and sister excellent relationship with brother and sister regardless of kinship", although their kinship is only indirect and spiritual.
Is this how it should work, or is it a bug?