Familiar Ghosthood
Requires MAL22's Trait Tracker Injector by MAL22
First things first, keep in mind this won't allow ghosts to have pregnancies/babies by themselves, so you're going to have to rely on mods specifically for that or on creativity. There's also a shortcoming we need to consider: the game only really cares for traits at birth, not conception. That's beyond my control. So if a parent of your child dies when the pregnancy is already underway, the game will still consider that as the child of a ghost. The only work-around I could think of would be to add a risk of the children not being born ghosts at all, but since the point was to make ghosts for the whole family I hesitate as to whether people would be alright with that.
This isn't original, mind you, since it was a request, so full credit to any and all people who've modded ghosts before. Also note that since babies are objects and BORING, they’ll be born looking like regular object babies. Very boring. I recommend you age them up and use height sliders / poses if you want them pretty ghost family immersive pics, because the ghostly fun is only really visible at toddler+.
So how does it work? I know, the explanation is like 3 paragraphs late. But it's a set of clones of in-game ghost traits. This means they have no individual strings etc., it all relies on in-game content, for they are cloned and modified from the original ghost traits in the game. Aging is enabled for them as well, which means your born-ghost Sims can make it all the way to Elder without ever technically being alive! Woo!
They can also be resurrected by any resurrection method that uses trait removal by type since they are categorized as ghosts. I couldn't find whether there were resurrection methods that don't use that but knowing the Sims I fear there might be one somewhere, so please inform me if you encounter any issue on that aspect.
For some reason ghost traits are basegame so this should be basegame compatible, but naturally you won't encounter the ghosts that require causes of death limited to some packs.
You might also notice that despite that, I did not include for example the deaths that apparently came with High School Years. That's because as much as I love chaos I would rather not include them when I cannot test them to even know which are the correct ghost traits for those deaths. I was also initially going to include non-permanent ghosts because of how amusing it would be for babies to be born ghosts due to poor decisions made at the time of their births, but those traits wouldn't be basegame so while I made some clones, they were not implemented.
Doesn't override anything and requires no translation on account of using the strings of the original ghosts.
Known issues: The aforemention whoopsies of how in-game inheritance doesn't care about when the baby's parent(s) attained ghosthood.