E.G.

In Slaughterhouse-Five, Billy Pilgrim is informed by the Tralfamadorians that

their flying-saucer crews had identified no fewer than seven sexes on Earth, each essential to reproduction. … Billy couldn’t possibly imagine what five of those seven sexes had to do with the making of a baby, since they were sexually active only in the fourth dimension.

The Tralfamadorians tried to give Billy clues that would help him imagine sex in the invisible dimension. They told him that there could be no Earthling babies without male homosexuals. There could be babies without female homosexuals. There couldn’t be babies without women over sixty-five years old. There could be babies without men over sixty-five. There couldn’t be babies without other babies who had lived an hour or less after birth. And so on. (pp. 114-115)

How would we revise our views about the moral aspects of parenthood if we were to learn that the Trafalmadorian account of human procreation is true? I think the question is at least amusing and maybe also productive. Of course, much would depend on the details, and different versions of the account would cause us to revise our views in different ways. 

There is a widely felt Deadbeat Dad Intuition according to which, if you are the biological father of a given child, then you have a moral obligation to do quite a lot to aid the child (e.g., you have to provide financial support, etc.), even if you have no emotional connection with the child and even if you have never met the child.

If the Deadbeat Dad Intuition is (as I think) true, this might conceivably be because (i) in general, being causally responsible for someone's existence is a way of coming to owe them aid, and (ii) if you are someone's biological father then you are causally responsible for their existence.

However, as many have noticed and said, there are many ways of being causally responsible for someone's existence, and it's not obvious that they generally come with the same sorts of obligations that deadbeat dads have. For example, Sean Rad, the founder of Tinder, has a kind of causal responsibility for the existence of a very large number of children, but it's not at all clear that he owes those children anything in virtue of that.

In view of this, we might say that what's special about deadbeat dads is not just that they have any generic form of causal responsibility for the existence of their offspring, but that they are causally responsible in the specific way that biological parents are causally responsible for the existence of the offspring. We might use 'sexual responsibility' to refer to that specific form of causal responsibility.

If we say that (iii) in general, being sexually responsible for someone's existence is a way of coming to owe them aid, and (iv) if you are someone's biological father then you are sexually responsible for their existence, then we can explain the Deadbeat Dad Intuition without assigning a huge number of obligations to Sean Rad. It seems possible to me that many people implicitly accept the combination of (iii) and (iv), and that this is why the Deadbeat Dad Intuition is broadly attractive to people.

The Tralfamadorian account seems to imply not just that seven people are causally responsible for any given child, but that seven people are sexually responsible for any given child. So, if it is true that people implicitly accept (iii) and (iv), then perhaps we should expect that, if we were to learn that the Trafalmadorian account of human procreation is true, then we would come to think that, for any given child, there are seven people, not just two, who have obligations to ensure that that child is provided for. And if those seven people were somehow identifiable, then we might expect our society to create legal mechanisms for ensuring that such obligations are fulfilled.