Tony Tyler

Tony Tyler was the young child of Jackie Tyler and Pete Tyler and the younger/parallel brother of Rose Tyler.

Biography
In the time between Battle of Canary Wharf and the first journey to Bad Wolf Bay, Jackie had fallen pregnant. (TV: Doomsday) Two years later, Jackie jokingly stated that she had named her son 'Doctor' to tease the meta-crisis Doctor, before admitting his name was Tony.

Whilst Jackie was fighting the Daleks during their invasion of her Earth, she left Pete on the "nursery run" to look after Tony, implying that Tony was still at preschool age. (TV: Journey's End)

Behind the scenes

 * Due to the time difference between the two Earths, it is not clear how old Tony is at the time of Journey's End, although he's still young enough to require a "nursery line" on behalf of his father.