Grandchild

Grandchild was a name used to describe one's descendant, namely the child of one's child, where the subject in question would be the grandchild's grandparent. Each subsequent generation of grandchild was given the qualifier of "great", which was then compounded.

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

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