In my current game I'm controlling only one sim in a family, so I can tell you that they wouldn't get very far in their careers, assuming they even got a job to begin with. If I wasn't controlling anyone, the plumbing would all break down and not get fixed, and the refrigerator would break, as would the computer, TV, and radio. They wouldn't have any children, but if there was a baby before I ceased controlling them, the baby would be looked after -- eventually. I wouldn't expect much relationship drama, though.