Grandparent

Grandparent was a name used to describe one's ancestor, namely the parent of one's parent, where the subject in question would be the grandparent's grandchild. Each previous generation of the initial grandparent was given the qualifier of "great", which was then compounded.

As the father of Sylvia Noble, Wilfred Mott was the grandfather of her daughter Donna Noble. (TV: Partners in Crime)

William Pike was the grandfather of Harry Pike, and so the great-grandfather of his son Darius Pike. (TV: The Cambridge Spy, The Last Precinct)