Releasing a ghost who has no urn or gravestone
I've had it happen twice where playable sims died when I was playing another household. If you don't have an urn/tombstone, you can't release them as far as I know. If they are still part of the household, they won't go away either. But you can mitigate the damage they cause by giving them things to do and play them just like any other sim. Keep them busy and that will stop them from breaking things all the time. They will still break things from time to time but you can stop most of it by keeping them busy.
There are 2 other ways to resurrect ghosts that I use other than Ambrosia. But you have to have the packs. If you have ROM, a spellcaster that has learned the spell can cast Dedeathify on them. If you have Romantic Garden, then you can use the wishing well object. Both of those ways will fail sometimes but if you keep trying, you can resurrect them. It just takes time.
But if you don't have those packs then, Ambrosia is what you will have to use. If you don't want them on the lot you are playing, then move them to another household until you do have the means to make Ambrosia. Then bring them back and resurrect them. Keep in mind that when a sim is resurrected, that the days in their life stage will get reset to zero so they start over at that age, YA in your case.
If you just delete them, that will leave a hole in the family tree and it will be like they never existed.
Hope this helps.
