As a parent, I can tell you that thoughts of your own death become much less worrisome. The overriding fear is that your child dies. My heart really goes out to parents who have loss children as it seems like something that would be very difficult to recover from. I would freely trade my life for my childrens life.

Another part of this is the eventual loss of your parents. If your parents die while you are very young -- as you alluded to -- it can be very traumatic. As we get older and when your parents pass, you see it much more as part of the natural cycle. Particularly if it happens when you are in the 'parent' stage. You see that your own death is not as important as making sure you have passed on life to your children.

I think this process is also inexorably linked to why people become more spiritual / religious as they age.