The common example of the violinist analogy disagrees here. You are under no obligation to provide continuing physical support to another person, even one everyone agrees is fully grown/sentient/alive/etc. Similarly, you are under no obligation to donate your liver/kidney/blood, even if you already promised to do so, even if not doing so will cause someone's death. In every case except abortion, we respect medical bodily autonomy to an extreme degree. And indeed in other cases we often find it immoral to force someone to assist a family member's survival on an ongoing basis (see "Savior Siblings").

> I'm sure that any of those individuals, once born, would prefer to live regardless of circumstance.

Not always, lots of people desire medically assisted suicide. Blanket assuming that everyone desires to live regardless of circumstance is factually incorrect.