Tony Tyler was the young child of Jackie Tyler and Pete Tyler and the younger brother of Rose Tyler.
In the time between the Battle of Canary Wharf and the first journey to Bad Wolf Bay, Jackie had fallen pregnant. (TV: Doomsday) Later, after Tony's birth, Jackie jokingly stated that she had named her son "Doctor" to tease the Tenth 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. (TV: Journey's End)
He was evidently named after Jackie's uncle Tony. (AUDIO: Retail Therapy, Wednesdays For Beginners)