The only male child of the actor Yul Brynner, he built a peripatetic career as a writer, historian, novelist, playwright — and roadie for the Band.Rock Brynner, whose life as a road manager for the Band, bodyguard for Muhammad Ali, farmer, pilot, street performer, novelist and professor of constitutional history overshadowed what, for a lesser mortal, might be a more than sufficient laurel on which to rest — he was the son of the actor Yul Brynner — died on Oct. 13 in Salisbury, Conn. He was 76.Maria Cuomo Cole, a close friend, said the cause of his death, in a hospice, was complications of multiple myeloma.Like many children of the rich and famous, Mr. Brynner led a charmed life. His father, a Russian émigré, was best known for his starring role in both the stage and screen versions of the musical “The King and I,” and later played lead Hollywood roles as a gunfighter, a Russian general and, in “The Ten Commandments,” Pharaoh Rameses II. A-list glamour encircled the son: Liza Minnelli was a lifelong friend from childhood; Elizabeth Taylor came to all his parties. The French poet and playwright Jean Cocteau was his godfather.But Rock Brynner did more with his silver spoon than most. A gifted student, he attended Yale, Trinity College Dublin and Columbia, where he received a doctorate in American history in 1993 before teaching for over a decade at Marist College, in Poughkeepsie, N.Y.In between his stints on campus, he shifted in and out of various milieus and demimondes. He wrote a one-man play based on Cocteau’s addiction memoir, “Opium,” which he performed briefly on Broadway in 1970. Afterward he traveled around Europe as a mime, a period in which he struggled with his own drug and alcohol problems — a theme that fueled his first novel, “The Ballad of Habit and Accident” (1981).Mr. Brynner, left, with his father, the actor Yul Brynner, and the entrepreneur Isaac Tigrett at the opening of the Hard Rock Cafe in Manhattan in March 1984. When Mr. Tigrett opened the restaurant, he hired the younger Mr. Brynner to be the manager.Mitchell Tapper/Associated PressMr. Brynner had a penchant for falling into celebrity orbits. While still in Europe he joined the entourage of Muhammad Ali, who was on something of a world tour after being stripped of his heavyweight championship title over his antiwar stance. Ali called him his “bodyguard,” even though Mr. Brynner was much shorter and slighter than the deposed champ.“Who’d ever have thunk,” Mr. Brynner recalled Ali joking, “that the son of the pharaoh of Egypt would be protecting a little Black boy from Louisville?”Mr. Brynner was no mere hanger-on: He worked as Ali’s press liaison, and it was in part thanks to him, and his connections in Dublin, that Ali was able to fight a high-profile bout against Al “Blue” Lewis in that city in 1972.After returning to the United States and largely sobering up, Mr. Brynner made friends with Robbie Robertson, the guitarist and chief songwriter for the Band, and for a time drove the group’s tour bus.When Mr. Robertson expressed interest in making a rock documentary, Mr. Brynner, by his account, put him in touch with another friend, the director Martin Scorsese. The result, in 1978, was “The Last Waltz,” widely considered one of the best concert documentaries ever made.Mr. Brynner rarely stayed in a single role for long. One day in the early 1970s he was hanging out at a London hotel bar when he met an entrepreneur named Isaac Tigrett, who had an idea for a rock ’n’ roll-themed restaurant.The two became close friends, and Mr. Brynner and his father became early investors in the Hard Rock Cafe, founded by Mr. Tigrett and Peter Morton, whose father had started the Morton’s steakhouse chain. When Mr. Tigrett expanded to New York in 1984, he hired Mr. Brynner as manager. The restaurant was, for a time, the place to see and be seen in Manhattan, and Mr. Brynner proved more than capable of handling all the boldfaced names angling for a table.“He grew up with celebrities, traveled with celebrities,” Mr. Tigrett said in a phone interview. “He knew this scene well.”Mr. Brynner with Liza Minnelli during a party at a Manhattan restaurant in 1981. They had been friends since childhood.Ron Galella Collection, via Getty ImagesMr. Brynner managed to stay at the Hard Rock Cafe for a year before becoming restless once more. He had always wanted to own a plane, he told Mr. Tigrett. He and his father used their profits from the restaurant to open a charter air service, based at a small airport in Danbury, Conn., not far from the Westchester farm where Rock was now living in a guesthouse, free of charge in exchange for working its small field of vegetables.By the mid-1980s, with his wild days behind him, Mr. Brynner returned to his intellectual pursuits. He wrote a biography of his father, “Yul: The Man Who Would Be King” (1989), while completing his doctorate in American history at Columbia, with a specialty in constitutional history.The biography, which appeared four years after Yul Brynner’s death at 65, exploded certain myths that his father had told about himself (he did not, as he claimed, descend from Roma stock). But it also painted a portrait of a complicated man, whose immense ego sometimes got in the way of his genuine love for his only son — and of how that son struggled under the weight.“It is a study of how a son models himself on his father,” Rock Brynner said in a 1991 radio interview, “and then must distance himself later in life.”Yul Brynner Jr. was born on Dec. 23, 1946, in Manhattan. His father, still a struggling actor, was away in California looking for stage work, while his mother, Virginia Gilmore — who would also achieve cinematic fame — kept house in a small apartment on East 38th Street, above a dry cleaner’s.There was no question what the boy’s first name would be: “In our family,” Yul Brynner Sr. said, “Yul is not just a name. It is a title.” But he also gave his son the nickname Rock, after the boxer Rocky Graziano, in a bid to toughen him up for the rough streets of New York.Rock lived a wandering childhood, following his father’s career from New York to Chicago to Los Angeles and, finally, to Switzerland, where he attended the International School of Geneva, a famed boarding school.He enrolled at Yale, but after a year transferred to Trinity College Dublin — in part because, he later said, he was enthralled with the work of Samuel Beckett, whom he had met, and that of James Joyce, who might be one of the few 20th-century notables whom he did not.He graduated with a bachelor’s degree in philosophy in 1969 and received a master’s in the same subject, also from Trinity, in 1972.Mr. Brynner’s marriage to Linda Ridgway, in 1973, ended in divorce. He married Elisabeth Coleman in 1978; they also later divorced. He is survived by his sisters, Victoria, Mia and Melody Brynner and Lark Bryner, who uses the original spelling of the family name.Mr. Brynner explored his family’s Eastern Russian roots in a 2006 book.via Distinct PressAfter receiving his doctorate, Mr. Brynner taught at Marist and at Western Connecticut State University. He also continued to write. Along with another novel, “The Doomsday Report” (1998), a prophetic satire about climate change, he wrote about the controversial drug thalidomide (“Dark Remedy: The Impact of Thalidomide and Its Revival as a Vital Medicine,” 2001); his family’s roots in eastern Russia (“Empire and Odyssey: The Brynners in Far East Russia and Beyond,” 2006); and, with Andrew Cuomo, the brother of Maria Cuomo Cole, who was governor of New York at the time, state water policy (“Natural Power: The New York Power Authority’s Origins and Path to Clean Energy,” 2016).Thanks to his research on eastern Russia, the State Department sent Mr. Brynner on several lecture tours in the region. There he paid tribute to his family by helping open a Brynner museum and unveil a statue of his father in Vladivostok, where the elder Mr. Brynner was born.“Yes, it’s difficult for the children of iconic figures to establish independent identities,” he told The New York Times in 2001. “But with all the suffering in this world, I wouldn’t shed too many tears for those who had privileged youths.” More