What Happens if YOU die?

I had an essay published yesterday in More.com, something anyone can do, so its kinda cool. It raises the issue that I am sure many single parents go through, particularly ones where one parent is not in the picture in any way, either through death or abandonment, where the kids become anxious that something is going to happen to their sole parent. Its an issue that I am often dealing with, so much so that I have had to get my son professional help for anxiety. It played into the issue I has having recently with regards to sleepovers. But maybe, its just something all kids go through. Its my perpetual question: Is this normal kid behavior, or is it grief-related?