great-nibling-in-law Share definition Flag 1. The grandchild-in-law of one's sibling. 2. The grandchild of one's spouse's sibling. My great-nibling-in-law is a good person. great-nibling-in-law by Elivaldeq November 24, 2019 0 0 Get merch Get the great-nibling-in-law mug. Buy Now — $32.95 See more merch