Nibling - Noun
Nibling is a term used for nieces and nephews without an associated gender (intersex, non binary, etc)
It can also be used as a plural for multiple nieces and nephews without the need to say both
Who are my favorite niblings?
The grandchild-in-law of one's spouse's sibling.
My co-great-nibling-in-law is a good person.
Child of a paternal half-sister with maternal half-brother or child of a maternal half-sister with paternal half-brother.
My double-half-nibling is a good person.