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. (TV: Partners in Crime) Each subsequent generation of grandchild was given the qualifier of "great", which was then compounded. (TV: The Cambridge Spy)

Susan Foreman was the First Doctor's granddaughter. (TV: "An Unearthly Child")

As the daughter of Sylvia Noble, Donna Noble was the granddaughter of her father Wilfred Mott. (TV: Partners in Crime) Donna's daughter Rose was therefore Wilfred's great-granddaughter. (PROSE: )

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)

Steven Carter was the grandson of Jack Harkness. By 2009, Jack appeared younger than his daughter and Steven's mother, Alice Carter. Because of this, Alice led Steven to believe Jack was actually his uncle rather than explain his grandfather's immortality. (TV: Children of Earth: Day One)