And so you just know they are unhappy? You know parents also have kids up and move away too. There is no guarantee that they will keep you company in old age or even be around.

As a childless person I'm very happy in my mid to later life to be able to travel frequently, to see my nieces and nephews, and to do what I like like my own hobbies. Don't be so quick to assume that they must be unhappy.