The first brother, Pierre-Antoine Cousteau, became a journalist, propagandist, racist and Nazi sympathiser. He was jailed as a traitor to the country that he adored. He died in disgrace in 1958.
The second brother, Jacques-Yves Cousteau, became a national hero, an international superstar, a self-appointed saviour of the planet. His sea-worn face, reassuring voice and red beret came to symbolise, to millions of people, a love of adventure, a love of animals, a love of humanity, a love of the ocean, and a selfless devotion to the new, ecological religion of the 1970s and 1980s.
But even before his death - two years ago yesterday at the age of 87 - doubts had begun to surface about "Jacques" Cousteau, as he was always known in the English-speaking world: doubts about his treatment of animals; about his treatment of his family; about the veracity of some of his documentaries, beginning with his celebrated 1969-79 series, The Undersea World of Jacques Cousteau.
Since his death, his organisations - l'Equipe Cousteau in France, the Cousteau Society in the United States - have been blown from one financial reef to another, under the uncertain helmsmanship of his former mistress and second wife, Francine. The French part of the empire lost pounds 600,000 last year. The difficulties have been compounded by the deep obscurity of Cousteau's finances, a tangled net of private wealth and public and charitable activities.
There are fears that the entire Cousteau operation - once an autocratic, one-man rival to Greenpeace - may shortly disappear below the waves. The captain's last dream - a new hi-tech, eco-trouble-shooting vessel, the Calypso II, to replace his legendary converted minesweeper - has been shelved indefinitely.
Worse, new evidence revealed this month by the newspaper France-Soir suggests that the "saintly brother" - at least at one stage in his life - shared some of the same racial opinions as the "frere maudit", the accursed brother. In a letter he wrote to his best friend in May 1941, Cousteau complained that he and his family could not find a decent apartment in Marseilles because of all the "ignobles youpins" (vile yids) pouring into the city.
The letter was written at a time when thousands of French Jews were fleeing to the south to escape persecution by the Nazi occupiers of northern France; it was written after the Vichy government had promulgated anti-Semitic laws which led, within months, to the rounding-up of tens of thousands of Jews and their deaths in concentration camps. Defenders of Cousteau have pointed out in recent days that his sentiments were widely shared in the France of that period: that the letter says more about France in 1941 than it says about Cousteau.
Maybe. It does, however, cast a powerful beam of light on one submerged wreck - Vichy France - that Cousteau preferred in later life to leave unexplored. The world's favourite Frenchman often claimed that he had served in the Resistance and that his Legion d'Honneur had been awarded for his wartime activities. It was, but for wartime activities on behalf of Vichy, spying on the Italians in 1941. The rest of the war Cousteau, although nominally still a naval officer, spent launching his own career, using his collaborationist brother's connections to acquire the materials he needed to perfect a revolutionary method of diving and to acquire raw film.
His first work - Par Dix-Huit Metres de Fond (Eighteen Metres Beneath the Waves) - was given its premiere in 1943 by a German association, Internationaler Kultur Film, before an audience of German officers and Vichy officials at the Theatre de Chaillot in Paris (contrary to his later reputation as a conservationist, the film was about underwater hunting and fishing, Cousteau's obsession at the time).
All of these facts, save the revelation of the anti-Semitic letter, were first revealed in 1993 in an excellent biography of Cousteau - by no means entirely negative - written by one of the best French investigative biographers, Bernard Violet. His book produced new evidence to back up earlier allegations that the Cousteau team had - under pressure from Hollywood to produce neat, anthropomorphic story lines - mistreated, and even accidentally killed, some of the sea creatures that his television series transformed into international celebrities.
It also explored some of Cousteau's less known activities, including his work for, and subsidies from, international companies which "le Commandant" simultaneously attacked as "the biggest polluters on the planet".
So what remains of Cousteau's reputation? Was it just a question of 20,000 lies under the sea?
Not entirely. Cousteau invented deep-sea diving, as we know it today. He was the co-inventor, in 1943, of the aqualung, which made it possible for the first time to descend into the depths without air lines and cumbersome suits. He helped to develop underwater filming techniques, which had been rudimentary until that time. His early films - especially The World of Silence, his 1953 Oscar and Cannes Palme d'Or winner - were stunningly lyrical presentations of an undersea world previously unknown and unsuspected (the movie was masterminded by Cousteau and filmed by Louis Malle, who went on to become a great director in his own right).
Forty-six years later Le Monde du Silence is still one of the finest sea documentaries ever made, all the more impressive and satisfying for avoiding the anthropomorphic antics of the later adventures of, among others, the sea lions Pepito and Christobal (one of which died during filming).
Cousteau's biographer, Bernard Violet, who also uncovered the anti-Semitic 1941 letter, says: "There are many things which no one could, or should want to, take away from Cousteau. His work on the aqualung; his development of filming underwater; above all, the way he brought the two together. Cousteau did not steal his Palme d'Or or his Oscars. I have watched some of those early Cousteau films with an audience of eight- and nine-year- olds. The kids are transfixed; they don't move for 45 minutes.
"On the other hand, it is clear that Cousteau was also a liar, a cheat and a dissembler. He was a false scientist, a false ecologist and a false humanitarian. It is now also clear that he was a racist. The 1941 letter is part of a wider pattern. Since he died, I have been inundated with information from friends and former colleagues (including the letter). Cousteau liked in later life to present himself as a man in love with the human race, but his human relations were often appalling. The racist remark is not isolated. He would often make derogatory remarks about Arabs, whom he accused of overwhelming France."
Cousteau's eldest son, Jean-Michel, 61, was a frequent victim of his father's "appalling human relations". Jean-Michel made, virtually without his father's help, 55 movies for which Cousteau senior took all the credit. His only thanks was to be described as an "incompetent" when their underground ocean theme-park in central Paris - not a drop of water; lots of cardboard sharks and dolphins - went bust in 1992.
The park was mostly the older Cousteau's creation, but le commandant blamed his son. "It's not because a kid has been born from your sperm that he has the qualities necessary to replace you," Cousteau cruelly told the press. He later fixed things so that Jean-Michel would be excluded from running the empire at his death and everything would pass into the hands of a former flight attendant - Francine, his second wife and previously his mistress for 14 years.
Despite these slights, and other quarrels, Jean-Michel remains a stout defender of his father. "My father was a hard man. A strong man," he says. "There was little place for emotion. But his love for and his marvellous way of seeing the natural world were genuine."
It is also true that the minds of a whole generation of young people were opened to the beauties of nature - and the urgent need to preserve them - by Cousteau's films (whoever actually made them and however mawkish some of them may have been).
In his earlier years, Cousteau allowed the sea and sea creatures to be the heroes of his movies. In later years, there is a different, more strident, almost megalomaniacal tone. "Cousteau was a man of action, an adventurer, perhaps the last great adventurer of the century," said Mr Violet. "But he ended up weaving a web of half-truths and outright lies which presented himself as something more grandiose than that."
Cousteau came to see himself as the hero of the movie of his own life: the man who could telephone prime ministers and presidents; the man who made ex cathedra, often ignorant and contradictory pronouncements on everything from nuclear power to growing food on the ocean floor.
One of his last great projects was a manifesto of the "rights of future generations", which he hoped to have adopted by the United Nations. However, the man who wanted to "safeguard the planet for thousands of years into the future" left his own professional and private affairs in such a mess that his organisation is already on the verge of collapse.
The reputation of Cousteau the film-maker and man of action will stand the test of time. The myth of the other Cousteau - the humanitarian eco- saint - has scarcely survived his death by two years.Reuse content