Spifftastic Boom.
Hang on a sec.
Don't cells have to duplicate to create a fetus? What about the duplicated cells? They weren't created before you existed, so how could they go back to what they were doing? Same thing, almost exactly: the constituent atoms of those cells would be doing something else. Everything beyond the atomic level, maybe some molecular structure, was synthesized organically in some way that involved you or your parents; cut out your grandfather and you're back down to your atoms. Not your cells, but your atoms. The duplicated cells are not created out of nothing; the original cells take in nutrients and oxygen from outside and form the new cell out of those; remove the original cell, and those nutrients and oxygen go back to doing whatever they were doing beforehand; if the nutrients were synthesized by you or the parent whose father you killed, those nutrients would also be rendered back into their constituent atoms.
Basically, nothing of you would still exist above the atomic level; you're not unmaking yourself as a human into just any sub-human portions, but rather unmaking yourself down to the very bottom, into inorganic substances that would exist with or without you. You're unmaking you, you're unmaking your organs, your tissues, your cells, your organelles, your proteins, your molecules, everything down to the atoms.