If you care about a person, then while you might not care as much if a recent duplicate or a recently duplicated person were lost, you would still care about as much if either of them suffers..

As is implied by my 'recently', the two will diverge, and you might end up with loyalty to both as distinct individuals, or with a preference for one of them.

Also, I don't think parents value each of newborn twins less because they have a spare.