Claude Ruiz-Picasso, who, after a legal fight that established him and his sister Paloma as legitimate heirs to their father, the great artist Pablo Picasso, managed his vast estate for more than 30 years, died on Thursday in Switzerland. He was 76.

His death was confirmed by his lawyer, Jean-Jacques Neuer, who did not give a cause or say where in Switzerland he died.

Claude and Paloma were the children of Picasso and Françoise Gilot, a French painter 40 years his junior, who, after a long and stormy relationship, left him in 1953. Picasso did not deny that he was Claude and Paloma’s father, but he was so angry when Gilot published a memoir, Life With Picasso, in 1964 that he cut off contact with her and their children. Gilot died in June.

In 1970, Claude Ruiz-Picasso and Paloma Picasso sued in a French court to be recognised as Picasso’s legitimate children. French law changed in 1972 to give children born out of wedlock rights of inheritance; the siblings won a court ruling in March 1974, almost a year after their father’s death, to further establish their legitimacy. The court said Picasso had confirmed his paternity by dedicating paintings to them.

By then, Claude Ruiz-Picasso had been living in New York City since 1967. Over the next seven years, he studied at the Actors Studio; worked as an assistant to fashion and portrait photographer Richard Avedon; and began a career as a photojournalist.

Ruiz-Picasso’s work eventually appeared in Vogue, Saturday Review, Time and Life magazines. He said he had been inspired by photojournalist David Douglas Duncan, who spent years creating a pictorial record of his father.

“Duncan was always around, clicking away, and I thought, oh, this would be an interesting occupation,” Ruiz-Picasso told Picasso biographer John Richardson in an interview for Gagosian Quarterly, an art-world magazine published by gallery owner Larry Gagosian. “When I was about 17,” he added, “he very kindly gave me a professional camera.” It was a Nikon.

Claude Ruiz-Picasso was born on May 14, 1947, in Neuilly-sur-Seine, France. (Ruiz was the name of Picasso’s paternal grandfather.) Paloma was born two years later. His half-siblings were Paulo, the son of Picasso’s marriage to ballet dancer Olga Khokhlova, and Maya Ruiz-Picasso, whose mother was Marie-Thérèse Walter. Paulo Picasso died at 54 in 1975. Maya Ruiz-Picasso died last year at 87.

In 1989, after six years of squabbling among all Picasso’s heirs including his widow, Jacqueline Roque, over the distribution of the thousands of artworks he left behind and the communal right to exploit his name commercially, a French court appointed Ruiz-Picasso the estate’s administrator.

“I never expected or desired to have any kind of role like this, or have any influence over my father’s legacy,” he told Richardson. “So because of the Picasso administration, little by little, I had to quit photography. Not all of a sudden but little by little.”

New York Times News Service