Uncle

The Doctor's uncle on Gallifrey was known as the Uncle. (GAME: The Eternity Clock, TV: Time and the Rani)

The uncle of Peter and David was a human inventor of time travel (PROSE: Timechase)

Watkins was the uncle of Isobel Watkins. (TV: The Invasion)

Federico was the uncle of Giuliano. (TV: The Masque of Mandragora)

Tim Latimer's uncle had a six month posting in Johannesburg. (TV: Human Nature)

Digby was the uncle of Cyril and Lily Arwell. (TV: The Doctor, the Widow and the Wardrobe)

Other references

"Bob's your uncle" was a British idiom. (TV: Hide)

Uncle Sam was a figure associated with the United States of America. (TV: Dreamland, The Sound of Drums) In 1959, CIA agent Jerome Weismuller claimed that a radio destroyed by Gavrok of the Bannerman was "property of Uncle Sam", to which Gavrok asked where their uncle Sam was as Hawk attempted to correct him. (TV: Delta and the Bannermen)

Uncle was an entrepreneur and crime lord from New Memphis (PROSE: Judgement of the Judoon)

Alongside Auntie and Nephew, Uncle was a servant of House (TV: The Doctor's Wife)

Within the Dalek City on Skaro, the Twelfth Doctor quipped to Davros that his personal chamber was "exactly where you dump a smelly old uncle / family pet / genius scientist who couldn't even invent legs." (TV: The Witch's Familiar)