Children are great for reminding us of our mortality

So my son, who is 4, and rather cute, tells me in his bubbly-cheery voice "Dad!  When I'm a daddy, you will be the grandpa!"

I know he's just learning his family roles & relationships, but this particular comment struck me as purely morbid.  He may as well have said "dad, when are you going to pay for your funeral arrangements so we're ready - for you to die?"