That pontification just feels pulled out of thin air.
Suppose I just need S to take over the family fortune? Also pulled out of thin air.
You know, like, if you don't take a loan, you don't owe any money on that loan, it's not like there is already loans made in your name, with debts waiting to be paid off, that you must go to the bank and take, so that you can pay them off.. I don't know how many different ways there is to say the same thing, but if the _THING_ does not exist, then it really has no rights, and you really have no duty towards it.. Those start only if you make the thing exist..
If you have a fortune, and nobody to inherit it, then you don't have any obligation to create a heir, you can chose to do that (even if I argue that it's morally bad to do, I will amend that it's probably less morally bad to do than if you created them so they could inherit the debt you don't have enough time to pay off during your own life)
That part is obvious and incontrovertible.
The idea that such a duty must exist, or is even relevant, is just something someone made up.