The point is that the analogy actually shows the opposite of what you want it to show! Family members are very, very weak copies of each other, and they still s

The point is that the analogy actually shows the opposite of what you want it to show! Family members are very, very weak copies of each other, and they still sacrifice themselves to save other family members. Explicitly, we have weak evidence against "There's no rational reason at all to think a copy would be more willing to die", namely that the better the copy of you, the more likely you are to sacrifice yourself for them. (Would an average human be more willing to die for their third cousin twice removed, their aunt, or their father?) The evidence is weak, naturally, because nature doesn't contain anything even remotely like two exact copies of a person; all we can do is attempt to extrapolate from the obvious trend that "the closer the relation, the more willing I am to die for them", and the obvious extrapolation is "the closest possible relation - the exact copy - is the most likely candidate for me to sacrifice myself to save". By the way, the reason I downvoted your comment was because of the "you're projecting", which comes across as snarky and is not remotely implied by the parent comment.