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