Normally the needs of sims outside your family will not drop or degree at all. That's the reason why they won't starve. They will react 'normally' when one of your sims visit them. Then they can and will make food, use the shower, toilet, etc.
Some of them have jobs btw. They work in the shops where your sims buy food or relics.
My game was bugged once and when my sims where traveling to China the game forgot to actually takes the sims with me so when I arived my sims where still at home. And so the game picked a new family for me to play with: one of the Chinese sims.
The fact is, even with that family, the work panel doesn't came up, because 'I didn't have to worry about work while on vacation.' Anyway, those sims do work, when they are not selected.
