PARIS, March 20— Robert-Jean Longuet, a lawyer and journalist who was a great-grandson of Karl Marx, has died in a Paris hospital, his family said today. He was 85 years old.
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A non-Communist who became a supporter of de Gaulle in World War II, Mr. Longuet was repeatedly approached by Communists who told him that he belonged in their ranks. But Mr. Longuet used to reply brusquely: ''No. You have falsified my great-grandfather.'' Relatives said Mr. Longuet died Thursday, but did not give the cause of death.
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