0C4R

Zeroth-cousin-four-times-removed:
1- great-great-grandpibling (great-great-grandparent's sibling)
2- great-great-grandnibling (sibling's great-great-grandchild)

My great-great-grandpibling is my 0C4R in theory and my great-great-grandnibling is also my 0C4R in theory.

nibling-in-law

1- Nibling's spouse.
2- Spouse's nibling.

My nibling-in-law is a good person.

pibling-in-law

1- Pibling's spouse.
2- Spouse's pibling.

My pibling-in-law is a good person.

N1C3R

Negative-first-cousin-thrice-removed: great-grandparent or great-grandchild.

My great-grandparent is my N1C3R in theory and my great-grandchild is also my N1C3R in theory.

N1C4R

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

My great-great-grandparent is my N1C4R in theory and my great-great-grandchild is also my N1C4R in theory.