Lieutenant-Colonel Andrew Blodgett "Monk" Mayfair is an American industrial chemist, whose physical appearance tends to be compared to that of some kind of ape. He is one of Doc Savage's Fabulous Five Assistants, and it can be said that he and Ham Brooks are Doc's chief lieutenants.
In Tarzan Alive, Philip José Farmer identifies Monk as a member of the Wold Newton Family; specifically, as the nephew of Professor Challenger (who finds an almost exact double of himself in an ape-man in The Lost World). Monk's parents are identified as an American named Blodgett Mayfair and a Scotswoman, Melissa Rutherford.
In his article Monk, Son of Opar, "Dr Hermes" suggests that Monk's actual father was a brutish, ape-like Oparian male, and his mother was a Mayfair who was of a party that stumbled across the Lost City. In his article The Challenging Rutherfords, Brad Mengel cites fellow-Wold Newton scholar Dennis Power's theory that in fact Monk's father Blodgett Mayfair and his sister (Monk's aunt) were the offspring of one Anthony Mayfair, who discovered the lost city and carried off one of the beautiful female inhabitants to be his bride.
Mr. Mengel states further that Monk was married and divorced (which does not come into the pulps), and had two children, William Greir Mayfair and Anastasia Mayfair. Having taken his stepfather's surname, William "Pauncho" Greer Van Veelar is one of the assistants to Doc Caliban in the books by Philip José Farmer.
Mr. Mengel has also considered the appearance of a criminal with the same name as Monk in a Captain America novel, The Great Gold Steal by Ted White, although he is unable to confirm whether Monk or another man is actually the father (although Monk is said to be named on the birth certificate).
Farmer and Hermes together note that the original Doc Savage pulps suggest that the Mayfairs are of British extraction, and that Monk is related to the Canadian Mayfair family who are in line of the succession to the (fictitious) Earldom of Chester, Essex and Cornwall (all of which titles are already spoken for). In his article In What Years were Pat Savage and the Five Aides Born?, Arthur C. Sippo raises a - perhaps fringe - theory which associates Monk, Challenger, and Edward Hyde with a mysterious 'Lord Mayfair' featured in the family tree of the Mayfair witch clan, in the novels of Ann Rice.