Steven Carter

Steven Carter was the son of Joe and Alice Carter and the grandson of Jack Harkness and Lucia Moretti.

Profile
Steven's mother described Jack as his uncle as she wanted not to explain to him Jack's immortality and agelessness. The two appeared close, although their contact was infrequent. As Jack needed a child to defeat the 456, Steven was used to reverse the signal and kill the lone representative of the 456 on Earth, without explaining the situation to Steven. By reversing the signal, Steven, as Jack knew he would, died. His mother cradled his dead body tearfully as Jack watched. His mother, Alice, seemed not to forgive Jack for forcing Steven to sacrifice himself. (TW: Children of Earth: Day Five)

Behind the Scenes
Steven's death was the first death of a child seen onscreen in the Doctor Who Universe.