I spoke too soon :(

Any mods in your game? If you have WW for example, that was causing save data partial resets and rollbacks, so go update that if you have it. And if you haven't updated your game install to latest patch the aging bug was causing your entire game full of sims to age up every time you entered CAS or switched zones or something, so all that could have aged your families into death without you even noticing, while you were off playing some other family.

If the aging bug hit you there's no fix to bring back the dead families, should you not have backed your old saves up before bug hit your game.

If you do have mods and CC - go through your mods list and update all that have been updated -

https://forums.thesims.com/en_US/discussion/1001789/broken-updated-mods-cc-july-26-22-sexual-orientation-high-school-etc-patch

https://simsvip.com/2022/07/26/broken-updated-mods-high-school-years-ep/

Remove any mods that are broken but haven't yet been updated.

Make sure you delete the localthumbcache.package file after updating your mods (or removing/adding mods).