Susan Foreman's grandchildren

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

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. Susan brought her grandchildren to the rendezvous point in a pram. Upon seeing him, they gleefully shouted "Great-great-grandfather!". (NOTVALID: Doctor Who? 136)

Behind the scenes
Although Susan's grandchildren are depicted as babies 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 they are much older in actuality.

Multiple later sources showed Susan to have had children in her life after the Doctor, either by birth or adoption, but this is the only story ever to depict her with grandchildren.