Tony Tyler

Tony Tyler was the young child of Jackie Tyler and Pete Tyler, and the younger brother of Rose Tyler. In the time between Battle of Canary Wharf and the first journey to Bad Wolf Bay, Jackie had fallen pregnant. (DW: Doomsday) Two years later, Jackie jokingly stated that she had named her son 'Doctor' to tease the meta-crisis Doctory, before revealing that the child's name was Tony. Whether this is short for 'Anthony' is unclear. (DW: Journey's End)

Considering that around half a year elapsed in N-Space while three years elapsed in Pete's World (DW: Doomsday), 12 years should have elapsed in Pete's World between Doomsday and Journey's End. However, while Jackie was fighting the Daleks, she left Pete on the "nursery run" to look after Tony, implying that Tony is still at preschool age.

Tony has the rare distinction of being the offspring of two individuals from different realities.