Gwen Cooper's son

From Tardis Wiki, the free Doctor Who reference

By January 2021, Gwen Cooper had a son. Gwen told Jack Harkness that she fought off a Dalek with his boxing gloves, as well as a moped.

While his age is not given, the fact the boy has boxing gloves suggest he may at least be 5 years of age (so he can comprehend how to use them) (TV: Revolution of the Daleks)