Harry Sinclair's son

From Tardis Wiki, the free Doctor Who reference

The son of Harry Sinclair was born at some point after his aunt Helen Sinclair left England to travel with the Eighth Doctor in 1963.

Because of her "disappearance," he never met his aunt, who in turn only learned of her nephew's existence upon visiting her brother George in 1998. After his father died a few years before 1998, Harry Sinclair's son rarely met up with his uncle George. (AUDIO: Absent Friends)