 Sources vary in the canon of the "Thunderbirds" series as to John's age and birth date, although one written source suggests that he was born on 28 October 2041—this would make him the third son.The majority of sources and two decades of Thunderbirds calendars cite John's birthday as 8 October and he is 24 years of age.Chris Bentley, author of "The Complete Book of Thunderbirds", erroneously cited Gerry Anderson as the source of the misinformation about the birth order of the Tracy brothers, but later admitted that he was using the order of the brothers as shown in the credits.