Mr. Barnaby was the father of Tom Barnaby and a mentioned-only character in the episodes Sauce for the Goose and The Made-to-Measure Murders until Fit For Murder, where he makes a briefly appearance in Tom's mind.
Barnaby Senior married the sister of Alice Bly before the 20th April 1943, on which day they welcomed their only child Thomas Geoffrey Barnaby. Young Tom may have been named after his paternal grandfather.
Barnaby Senior had at least one sibling - Ned Barnaby who may have been fairly younger than him, as Ned's son John was at least twenty years younger than Tom.
- In the novel of The Killings at Badger's Drift, Barnaby Senior was a supporting character but he was adapted out of the TV adaption and wasn't referenced until Sauce for the Goose.
- John Barnaby was simply refered to as Tom's cousin in The Sword of Guillaume so it can be assumed Ned is Barnaby Senior's brother