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