They are, in essence, Tuvix's deceased parents.
If they were dead they can't be resurrected. That's why it's such a neat dilemma.
And, as was asserted in the episode itself, Tuvix is, by any reasonable definition, a separate and unique individual.
And when nessecery to save the mother, often an infant is allowed to die or aborted.
I really wish the episode had been better written with more analogies. Or the crux even rewritten. With Janeway having to choose between someone who has actually been born, and has a life rather than an accidental creation like Tuvix.
I haven't watched the ep in a while. Couldn't Tuvix have just claimed that he *was* Tuvok and Neelix merged together, and that they liked being together? I don't see a problem here other than Tuvok has to be the ship chef now in his offtime.