"The Doctor's Children of Time" was the name given by Dalek Caan and Davros to the group of people, consisting mostly of the Tenth Doctor's companions, who opposed the Daleks' plan to destroy all of reality.
Davros believed that the Children of Time were transformed into weapons and murderers by the Tenth Doctor, something the Doctor did not find the strength to deny. However, after Davros was defeated, Sarah Jane Smith, one of the purported Children, tried to convince him of a more positive spin on the concept, warmly telling him that he shouldn't "act like such a lonely man" because he had "the biggest family on Earth".
Dalek Caan predicted that one of the Children of Time would "die". Eventually, this prophecy became true in a manner of speaking when the Doctor erased Donna Noble's memories of him and her time in the TARDIS. He told Wilfred Mott and Sylvia Noble that "that version of Donna" was "dead". (TV: Journey's End)
The First Doctor earlier referred to himself and Susan, both Time Lords, as "children of time". (AUDIO: The Destination Wars)