Antiphus was a grandson of Cressida (formerly known as Vicki Pallister) and Troilus.
On one occasion, the Doctor's TARDIS materialised in Cressida's olive grove in Carthage and was found by Antiphus, who immediately ran to tell his grandmother. He observed Vicki leave briefly in the TARDIS before she appeared again just a minute later. (AUDIO: Fugitive of the Daleks [+]Loading...["Fugitive of the Daleks (audio story)"])
Behind the scenes
It is heavily implied that it is Antiphus' father who is Vicki's son (rather than his mother), given that she made a special request for Antiphus to tell his father that she loves him if she doesn't return.