Kate Stewart's second child

By the time of the invasion of Missy and the Cybermen, Kate Stewart had a second child, (TV: Death in Heaven) the first having been Gordon Lethbridge-Stewart. (HOMEVID: Downtime)

This child was born sometime between 2011 - as Conall Wilson, due to officially change his name to Lethbridge-Stewart by deed-poll in that year, once lamented that "Oh, sure, there were other Lethbridge-Stewarts out there; cousins, and other relations, but only two of them were direct descendants of Alistair Gordon Lethbridge-Stewart; Aunt Kate and Gordy." (PROSE: Acceptance, and then Understanding) - and 2015, (TV: Death in Heaven) when Missy and the Cybermen invaded.