Igor Yourievitch Bogdanoff and Grégoire Yourievitch Bogdanoff, who sometimes spelled their surname Bogdanov, were born on August 29, 1949, in a castle in the town of Saint-Lary-Soulan, a ski resort in the French Pyrenees along the Spanish border.
Their father, Youri Ostasenko-Bogdanoff, was an itinerant painter who said he was descended from a Tatar prince and who fled Russia as a boy. They were raised by their maternal grandmother, Bertha Kolowrat-Krakowska, a former Bohemian Countess who had lost her title after an affair with Roland Hayes, a black American tenor who was touring France. Their daughter, Maria Dolores Franzyska Kolowrat-Krakowska, was the mother of the twins.
Igor’s first marriage, to the Belgian aristocrat Ludmila d’Oultremont, ended in divorce. He married Amélie de Bourbon-Parme, a model and descendant of Louis XIV, in 2009 in a star-studded ceremony at the Château de Chambord in the Loire Valley. They broke up in 2016.
The brothers are survived by their half-brother, François Davant, and their sisters Laurence, Géraldine and Véronique Bogdanoff. Igor also has a son, Dmitri, whom he had with the actress Geneviève Grad; his daughters Sasha and Anna-Claria and son Wenceslas, all from his first marriage; and his sons Alexandre and Constantin, from his second marriage.
The Bogdanoffs claimed to be geniuses from an early age, saying they had been given 190s on IQ tests from their childhood. They graduated in applied mathematics from the Paris Institute of Political Studies, also known as Sciences Po, and studied at the École Pratique des Hautes Études.
After “Temps X” ended in 1987, the Bogdanoffs wrote “Dieu et La Science” (1991), about the relationship between religion and science. It was a bestseller in France, but a lawsuit was filed by Trinh Xuan Thuan, an astrophysicist at the University of Virginia, who claimed they had plagiarized one of his books.
The brothers settled out of court in 1995, after they had started their postgraduate studies. They said they were motivated by their interest in the so-called initial singularity, the moment before the Big Bang, when all matter, space and time were condensed into an infinitely dense point.