I'd start with using the NRaas Mod collection and adding another Mod to remove the NPC social workers that take children away as that's what corrupted three of my earlier saves before I started playing Modded.I've had pets,vehicles and household objects in sim's family trees after Malcolm Landgraab got taken by the social worker for failing school.One sim in that save had his toilet for his mum and a fridge for his dad while my toddler's mum was the family dog and the cat was his dad.His child aged sister became his daughter after the save got corrupted.