1. The child-in-law of one's sibling.
2. The child of one's spouse's sibling.
My nibling-in-law is a good person.
Child of their maternal first cousin’s child with the paternal first cousin’s child or double-first cousin’s grandchild.
My double-great-cousin-nibling is a good person.
Nibling-in-law (only spouse's nibling).
My nibling-by-marriage is a good person.
My nibling-by-marriage-in-law is a good person.