"Grand parents?"
"Grandparents. It meant parents-of-the-parents, long ago."

"Back and back and back?" Jonas began to laugh. "So actually, there could be parents-of-the-parents-of-the-parents-of-the-parents?"
—Lois Lowry, The Giver
"But my dad had no grandparents. Not a single cousin. I've never met another Wayne in Gotham ever. Are we dealing with generations of only childs marrying other only childs, with grandparent suicide pacts?"
Damian Wayne on this trope, Shortpacked