Have you done a whole reset on the town? If not try - resetsim *
Try going into CAS with testingcheatsenabled true then going back out? Or in CAS try aging them back to their previous life stage the click the undo button?
Found that problems like this can sometimes be helped if you move the household out using edit town and place them back in.
Strange problem, never had it before....
Let me know how it goes for you.