The Austrian philosopher and Vienna Circle member Herbert Feigl wrote about nomological danglers. Mental states as the epiphenomenalist conceives them have causes, but no effects. They are caused by physical states of the body and brain, but dangle nomologically in that there are no laws that relate mental states to physical states.
The childless are anthropological danglers. They are life's epiphenomena. They have ancestors (causes) but no descendents (effects). Parents are essential: without them we could not have come into fleshly existence. But offspring are wholly inessential: one can exist quite well without them.
There is a downside and an upside to being an anthropological dangler.
The downside is that it unfits one for full participation in the life of the community, removing as it does weight and credibility from one’s opinions about pressing community concerns. As Nietzsche writes somewhere in his Nachlass, the man without Haus und Hof, Weib und Kind is like a ship with insufficient ballast: he rides too high on the seas of life and does not pass through life with the steadiness of the solid bourgeois weighted down with property and reputation, wife and children. What does he know about life and its travails that his say should fully count? His counsel may be wise and just, but it won't carry the weight of the one who is wise and just and interested as only those whose pro-creation has pro-longed them into the future and tied them to the flesh are interested. (inter esse)
The upside to being an anthropological dangler is that it enables one’s participation in a higher life by freeing one from mundane burdens and distractions. In another Nachlass passage, Nietzsche compares the philosopher having Weib und Kind, Haus und Hof with an astronomer who interposes a piece of filthy glass between eye and telescope. The philosopher's vocation charges him with the answering of the ultimate questions; his pressing foreground concerns, however, make it difficult for him to take these questions with the seriousness they deserve, let alone answer them.
Someone who would be "a spectator of all time and existence" ought to think twice about binding himself too closely to the earth and its distractions.
Another advantage to being childless is that one is free from being an object of those attitudes of propinquity -- to give them a name -- such as embarrassment and disappointment, disgust and dismissal that ungrateful children sometimes train upon their parents, not always unjustly.
The childless can look forward to a time when all of their blood-relatives have died off. Then they will finally be free of the judgments of those to whom one is tied by consanguinity but not by spiritual affinity.
This opinion of mine will strike some as cold and harsh. But some of us experience more of the stifling and oppressive in our blood relations than the opposite. I do however freely admit that the very best human relations conceivable are those that bind people both by ties of blood and ties of spiritual affinity. If you have even one blood relation who is a soul mate, then you ought to be grateful indeed.
Related: SEP entry on Herbert Feigl