Susan Foreman's children

Susan Foreman's four children were the Doctor's great-grandchildren. At the time in which Susan and her descendants were visited by the Seventh Doctor and Ace, her children appeared to be in their childhoods.

The Seventh Doctor's close proximity to Susan and her family caused him to retro-regenerate into his first incarnation before the meeting they had arranged. Upon seeing him, Susan's children gleefully shouted "Great-grandfather!" to the Doctor and ran in his direction to give him a hug. (NOTVALID: Doctor Who? 136)

Behind the scenes
Although Susan's children are depicted as young children in ''Doctor Who? 136, the story depicts Susan herself without any visible signs of ageing after living for some years in the 22nd century as a result of being left there in The Dalek Invasion of Earth'' which leaves it possible the children are much older in actuality.

Published in 1988, Susan's children were portrayed much differently in later media. She and David Campbell were given three adopted children - Ian Campbell, Barbara Campbell and David Campbell Junior - in the 1998 novel Legacy of the Daleks, as well as one biological child in Alex Campbell who debuted in the 2009 audio story An Earthly Child. None of these characters appear to correlate to those seen in this story.