There are quite a few theories attempting to link Lupin and his extended family to other literary characters.
Lupin and Dupin are members of the same family
- The idea being that the same family of adventurers uses the family names Lupin and Dupin interchangeably. And that Arsène himself is a grandson of C. Auguste Dupin, the Gentleman Detective created by Edgar Allan Poe. Starred in three short stories between 1841 and 1844. Which exlains the detective skills demonstrated by Arsène.
Lupin has half-siblings
- According to his origin story, Arsène is a son of gym teacher and petty criminal Théophraste Lupin and Henriette d'Andresy, disinherited member of a wealthy family. Neither parent actually raised him, paying foster families to take care of their son. The idea is that for Théophraste this was a pattern of behavior. And that he had further children taken care of in this way. And that some turned out to become extraordinary. Among them 1) The Nyctalope (Léo Saint-Clair), a Superhero with Enhanced Sight. Starred in his own series of novels from 1911 to 1955, written by Jean de La Hire. 2) Judex (Jacques de Trémeuse). A Superhero with Hypnotic Eyes. Master of Disguise and Escape Artist. Originated in a 1917 film serial. Went on to have appearances in various media. 3) The Shadow (Kent Allard). A Superhero with Psychic Powers.
Lupin is the father of Gaston Max
- Gaston Max was the protagonist of a series of novels by Sax Rohmer, which lasted from 1915 to 1943. He was a member of the Paris police but was often called to assist police agencies around the globe. He was also a Master of Disguise. The argument goes that he partly modeled himself after his father.
Jean Lupin and Tigris are the same person
- The novel The Revenge Of The Countess Of Cagliostro (1935) introduces the character of Jean Lupin, a son of Arsène who was kidnapped by Countess Cagliostro at an early age. Raised to become a weapon against his father, under the alias Felicien Charles. The two Lupins face each other in 1924. Both surviving the encounter, though the younger man is never mentioned again. The idea is that the boy eventually resurfaced as Tigris, the Villain Protagonist in a series of novels by Marcel Allain. Starting in 1928. Tigris was also a Master of Disguise.
Lupin is the father or grandfather of Prince Rudolf
- The novel The Woman With Two Smiles (1933) features Lupin having an affair with Olga, Queen of Borostyria. And the affair seems to result in a pregnancy, sometime during The Edwardian Era. Prince Rudolf was an early Arch-Enemy of The Saint, featured in three novels from 1930 to 1932. He was a charming man with a ruthless streak. And also head of a criminal agency. The idea is that Lupin left a legacy among the royalty of Europe.
Lupin is the father of Nestor Burma
- 'In 'The Barnett & Co. Agency'' (1928), Lupin poses as a seedy Private Detective with some success. Nestor Burma is a famous French Hardboiled Detective whose depiction has certain similarities to this type. He stared in a series of novels and short stories from 1943 to 1983. The idea is that Nestor models himself after an aspect of his father.
Lupin is the grandfather of Bob Morane
- Bob Morane is the protagonist of a long-running series of novels, starting in 1953 and still ongoing. A French veteran of World War II, though having spend most of the War serving with the Royal Aif Force, Morane has developed an expertise in several fields. Which have served him well in adventures ranging from the mundane to the fantastic. The argument going that he is continuing a family legacy of masterminds.
Lupin is the grandfather of Nick Jordan
- Nick Jordan was the protagonist of a series of Spy Fiction novels André Fernez, lasting from 1959 to 1968. He had a talent for international intrigue and above average abilities in various fields. Just like his alleged grandfather.
- Stated in the series, no less.