**TIP**
I know not everyone like to use the cheats but sometimes you gotta do what you gotta do.
I have seen alot of issues with the vampires dying when you move them into your household, before you move them in set your needs to static, then as soon as you ask them to move in and they do, the needs bar will be rising, giving you enough time to get them situated in your home. Then set the needs back to dynamic when your done.
Unless they are dying regardless? I will have to test this out, but it works with my vampires.