N1C8R

Negative-first-cousin-eight-times-removed: great-great-great-great-great-great-grandparent or great-great-great-great-great-great-grandchild.

My great-great-great-great-great-great-grandparent is my N1C8R in theory and my great-great-great-great-great-great-grandchild is also my N1C8R in theory.