They were the cheekbones, and chins, that dropped jaws at the Cannes Film Festival.



So high and bulbous as to appear to threaten their owners' vision, the twin sets of reportedly collagen-injected zygomatic bones that walked the red carpet at Cannes this week caused a stir around the world.



Who exactly were their owners, the French twin brothers Igor and Grichka Bogdanoff, and were they the male answer to socialite Jocelyn Wildenstein, whose own obsession with plastic surgery earned her the nickname "bride of Wildenstein"?



The story of the Bogdanoff brothers is as fascinating as their pouts are strained, spanning celebrity, academia, accusations of plagiarism and the mysteries of the universe.



The twins, now aged in their 60s, were best known in the late 1970s as the classically handsome hosts of French science-fiction series Temps X (Time X).



Described in The New York Times as "wunderkids" with high intelligence but inflated egos, the brothers courted controversy ever since.



Raised in a castle in south-west France, the brothers say they are descended from Russian and Austrian nobility, the newspaper says.



Both completed degrees in applied mathematics before moving into television, writing, producing and hosting Temps X during its successful decade-long run.



But in 1991 an American-based Vietnamese astronomer alleged the Bogdanoffs had plagiarised large sections of his work to produce their best-selling French book Dieu et la Science (God and Science).



The matter was settled out of court some years later, The New York Times reported, after the brothers counter-sued, alleging the astronomer borrowed material from their earlier works of fiction and non-fiction.



Two years later the twins embarked on post-doctoral studies, working under unconventional physicist Moshe Flato on a decade-long effort during which they shunned the limelight.



Grichka was granted a PhD in mathematics in 1999, but only just. He was awarded with an "honourable", the lowest passing grade.



Igor was less successful, having his first attempt rejected and only attaining his PhD in theoretical physics - again with an "honourable" pass - after publishing extra papers in peer-reviewed journals.



"These guys worked for 10 years without pay," the twins' second adviser, mathematician Daniel Sternheimer, told The New York Times in 2002.



"They have the right to have their work recognised with a diploma, which is nothing much these days."



But three years after attaining their qualifications, the academic world was rocked by rumours the Bogdanoff boys had staged a hoax, tricking their peers into awarding them doctorates with jargon-rich "complete nonsense".



The brothers defended their work and were backed by the Massachusetts Institute of Technology physicist who read and approved Igor's thesis, Roman Jackiw.



Dr Jackiw said he found their work speculative but "intriguing", while other academics claimed "the Bogdanovs don't know how to do physics".



Still, the twins moved on, re-inventing their television careers with a 21st Century version of Temps X, called Rayons X (X-Ray).



They deny ever having gone under the plastic surgeon's knife, with one French report suggesting a hormone disorder often associated with gigantism could be the cause of their blown-out features.



Photographs purportedly taken in the 1990s show the first obvious signs of the brothers' enlarging cheekbones, while growth in their lips and chins continued unabated throughout the last decade.



They hosted their Rayons X series as avatars, younger computer-generated versions of themselves, who interacted with a studio audience.



But the twins continue to make public appearances, most recently at an anniversary party for jeweller Chopard at Cannes, at which their chins, cheeks and lips resembled something out of the sci-fi novels the twins penned before they found fame.

GETTY STEPPIN OUT: The French twin brothers Igor and Grichka Bogdanoff at Cannes this week.