Friends knew him as Bobby Kennedy, and he was known to be at the head of what appeared to be a perfect family, including 11 children, until his assassination more than 50 years ago.
Larry Tye, author of new book 'Bobby Kennedy: The Making Of A Liberal Icon' spoke to Robert's widow Ethel Kennedy as well as others who were part of his inner circle to reveal that the late New York senator and U.S. attorney general may have been unfaithful in his marriage.
"Some who know him say that Bobby flirted (like other members of the Kennedy family), and may have been unfaithful," Tye said, but clarified, "I don't know whether or not Bobby cheated."
See photos of Robert F. Kennedy from throughout his life:
Robert F. Kennedy (life, assassination)
Robert F. Kennedy (life, assassination)
Sen. Robert Kennedy, center of picture, is roughed up from enthusiastic crowd May 4, 1968 as he carried his campaign for Tuesday's Indiana presidential primary into Black areas of Indianapolis. (AP Photo/Paul Shane)
U.S. Attorney Gen. Robert F. Kennedy is photographed in his office in Washington, D.C. on Aug. 28, 1964. (AP File Photo)
Attorney General Robert F. Kennedy and his wife, Ethel, leave the House Office Building after the attorney general presented to the House Judiciary Committee his report on the proposed increase of Federal judges on March 13, 1961. Mrs.Ethel Kennedy always attends her husbandâs appearance on Capitol Hill. She did it for years when he was the chief counsel for the Senate committee investigating âirregularitiesâ in union management activities. (AP Photo/John Rous)
16th March 1938: Joseph Patrick Kennedy (1888 - 1969), the American Ambassador and financier with his wife and five of their nine children at the Princes Gate home in London. Left to right: Kathleen, Edward (who became a Democratic senator), Joseph Kennedy, wife Rose Kennedy, Patricia (1924 - 2006), Jean and Robert, who became a Democratic senator before his assassination. (Photo by H. F. Davis/Topical Press Agency/Getty Images)
Massachusetts Sen. John F. Kennedy, left, compares notes with his brother and campaign manager, Robert Kennedy, on July 10, 1960 in an unknown location. The Senator is seeking the Democratic presidential nomination. (AP Photo)
Sen. Robert F. Kennedy, D-N.Y., told a Senate Judiciary Subcommittee, March 3, 1965, that he resented what he termed a false implication that he had done something improper as Attorney General. He appeared before the Senators at his request to deny that he had sought to plant magazine articles against persons under investigation by the Justice Department when he was Attorney General. (AP Photo/Henry Griffin)
circa 1964: Outside his residence at number 10 Downing Street, London, the British prime minister Sir Alec Douglas-Home, right, shakes hands with Robert Kennedy, US attorney general, and brother of the assassinated American president. Kennedy is in London for talks with the British government. (Photo by Kent Gavin/Keystone/Getty Images)
FILE - In this Aug.23, 1963 file photo, Sen. Edward M. Kennedy, D-Mass., center, poses with his brothers U. S. Attorney General Robert F. Kennedy, left, and President John F. Kennedy at the White House in Washington. The Kennedy image, the "mystique" that attracts tourists and historians alike, did not begin with his presidency and is in no danger of ending 50 years after his death. Its journey has been uneven, but resilient _ a young and still-evolving politician whose name was sanctified by his assassination, upended by discoveries of womanizing, hidden health problems and political intrigue, and forgiven in numerous polls that place JFK among the most beloved of former presidents. (AP Photo)
Attorney General Robert F. Kennedy, left, and Supreme Court Justice William O. Douglas are shown crossing a bridge five miles up the Elwha River trail as they hike into the Olympic National Park, Port Angeles, Washington, August 9, 1962. The Kennedy family and a party of friends left this morning and headed into one of America's most ruggedly beautiful areas on a four-day camping trip. (AP Photo)
Sen. Robert F. Kennedy, pushing his Democratic Presidential nomination campaign in the west, uses a bullhorn to amplify his failing voice, in an appeal from a Denver motorcade for help in his political challenge to President Johnson, March 28, 1968. Kennedy motored to a downtown arena after receiving throat treatment from his personal physician, Dr. James Gould, who was called to the Denver Airport from a skiing vacation 115 miles away at Aspen, Colorado. (AP Photo/stf)
Democratic Sen. Robert F. Kennedy of New York runs through the surf with his dog, Freckles, during a stop in Astoria, Ore., May 24, 1968, during his campaign for the presidential nomination. Kennedy was shot and killed by Sirhan Sirhan shortly after a California primary election victory speech on June 5, 1968, at the Los Angeles Ambassador Hotel. Bobby Kennedy served as campaign manager for his brother John F. Kennedy's successful presidential bid, and was later appointed by President Kennedy as U.S. Attorney General. (AP Photo/Barry Sweet)
Sen. Robert F. Kennedy, D-NY, shuts his eyes and paddles hard as he shoots some rapids during the last day of his trip down Idaho's "River of No Return," July 5, 1966. Senator Kennedy rode out the last 40 miles of the river in a kayak. The senator, along with his family and several friends, spent four days floating down the river in rubber rafts. (AP Photo/stf)
U.S. President-elect John F. Kennedy and Jacqueline Kennedy, holding their thirteen-day-old son, John F. Kennedy Jr., pose with relatives and friends after a baptismal ceremony at Georgetown University Hospital chapel in Washington, D.C. on Dec. 8, 1960. Sitting beside Jacqueline Kennedy is her mother, Janet Lee Auchincloss. The President-elect is sitting with Mrs. Bartlett, the baby's godmother, and her husband, Charles Bartlett. Standing are JFK's siblings, Jean Kennedy Smith and Robert Kennedy. (AP Photo)
Robert F. Kennedy, former U.S. Attorney General, holds the hand of his niece, seven-year-old Caroline Kennedy, as he walks from the airliner with his brother Edward Kennedy, left, on their arrival at London Airport on May 12, 1965. They arrived with their sister-in-law, Mrs. Jacqueline Kennedy to attend the dedication at Runnymede, Surrey, on May 14, of the memorial to John F. Kennedy, the assassinated U.S. president. (AP Photo/stf)
Members of the Kennedy family attend U.S. President John F. Kennedy's burial at Arlington Cemetary, in Arlington, Va. on Nov. 25, 1963. At center with veil is JFK's mother, Rose Kennedy; his brother Attorney General Robert Kennedy; and far right, his widowed wife, Jacqueline Kennedy. (AP Photo)
** FILE ** In this June 5, 1968 file photo, Presidential candidate Sen. Robert F. Kennedy speaks to campaign workers in Los Angeles minutes before he was shot June 5, 1968. At his side are his wife, Ethel, and his California campaign manager, Jesse Unruh, speaker of the California Assembly. As Presidential hopeful Sen. Barack Obama, D-Ill., moves ever closer to becoming America's first black president many worry about his safety. Supporters who see Obama as an inspiring, youthful advocate of change in the mold of Kennedy are mindful of Kennedy's assassination just two months after the Rev. Martin Luther King Jr. was killed. (AP Photo/Dick Strobel, File)
Sen. Robert F. Kennedy addresses a throng of supporters in the Ambassador Hotel in Los Angeles early in the morning of June 5, 1968, following his victory in the previous day's California primary election. A moment later he turned into a hotel kitchen corridor and was critically wounded. His wife, Ethel, is just behind him. (AP Photo/Dick Strobel)
Senator Robert F. Kennedy speaks to campaign workers, June 5, 1968, as his wife Ethel, left, and California campaign manager and speaker of the California Assembly, Jesse Unruh, look on, at the Ambassador Hotel in Los Angeles. After making a short speech, Kennedy was shot in an adjacent room. (AP Photo)
Charles Wright, a police technician, and officer Robert Rozzi inspects a bullet hole discoverd in a door frame in a kitchen corridor of the Ambassador hotel in Los Angeles near where Sen. Robert F. Kennedy was shot and critically wounded June 5, 1968. Bullet is still in the wood. (AP Photo/Dick Strobel)
Edward M. Kennedy with Ethel Kennedy and others at the airport in Los Angeles, June 6, 1968 as they depart with the body of the late Senator Robert F. Kennedy. (AP Photo/Harold Filan)
Two lines of mourners file past the casket of Sen. Robert F. Kennedy, D-N.Y., in New York City's St. Patrick's Cathedral the morning of June 7, 1968. (AP Photo/stf)
Mrs. Ethel Kennedy is escorted by her brother-in-law, Senator Edward Kennedy, to their pew in St. Patrick's Cathedral in New York for the funeral services of Senator Robert F. Kennedy, the morning of June 8, 1968. (AP Photo/stf)
A young boy touches the casket of Senator Robert F. Kennedy in paying respects June 7, 1968 near the main altar in New York's St. Patrick's Cathedral. An honor guard stands around the flag-draped casket of the Senator. The flag was placed by the Green Berets, members of the U.S. Special Forces. (AP Photo/stf)
Senator Robert Kennedy's funeral at St. Patrick's Cathedral in New York City on June 8, 1968. Services were conducted by Archbishop Terence Cooke. (AP Photo)
This is an aerial view of St. Patrick's Cathedral on Fifth Avenue in New York City as pallbearers carry the casket of Sen. Robert F. Kennedy from the church on June 8, 1968. After the service, a twenty-one car train carried the late senator and his family and friends 226 miles to Washington, D.C. He rests at Arlington National Cemetery. (AP Photo)
Jacqueline Kennedy, center, accompanied by her sister, Princess Lee Radziwill, left, pay their respects as they stand in front of Sen. Robert Kennedy's casket in St. Patrick's Church in New York City on June 7, 1968. In the center next to Mrs. Kennedy is Rev. Ralph Abarnathy and Andrew Young, right. (AP Photo)
Ethel Kennedy, escorted by her son, Robert Jr., and members of her family, are seen on the steps of St. Patrick's Cathedral after the funeral services of Sen. Robert F. Kennedy in New York City on June 8, 1968. The prelate at right with clasped hands is Archbishop Terence Cooke of New York. (AP Photo)
Sen. Edward M. Kennedy waves from the rear platform of the observation car bearing the remains of his slain brother, Sen. Robert F. Kennedy, as the funeral train passed through North Philadelphia Station, June 8, 1968. Others on platform are unidentified. (AP Photo)
Thousands filed past the grave of Sen. Robert F. Kennedy, marked by a plain white cross in Arlington National Cemetery, June 10, 1968. In the foreground, a guard carries a floral gift to a designated place at right of the grave. The umbrellas were used late in the day when a heavy rainstorm soaked the Washington area. The Senator's grave is near that of his brother, President John F. Kennedy. (AP Photo)
Jacqueline Kennedy and her two children, John Jr. and Caroline, kneel at the grave of Sen. Robert F. Kennedy, June 9, 1968 in Arlington National Cemetery, Arlington, Virginia. Both Robert and Jacqueline's husband John F. Kennedy were shot to death by assassins. Others are unidentified. (AP Photo/Henry Burroughs)
A family pay their respects at the John F Kennedy Memorial after the assassination of Senator Robert Kennedy, Runnymede, Surrey, England, 6th June 1968. (Photo by Tilbury/Daily Express/Hulton Archive/Getty Images)
6th June 1969: Mrs Stephen Smith and her daughters place flowers on the grave of her late brother, Senator Robert F. Kennedy following a memorial service at the grave site on the first anniversary of the late Senatorfs death. (Photo by Gene Forte/Keystone/Getty Images)
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Tye explained that extramarital affairs within the Kennedy clan are not unheard of, though frowned upon. Despite rumor of possible infidelity, Tye believed "(Bobby) was the most puritanical and sanctimonious of the Kennedy boys."
According to Tye, rumors surrounding the family has plagued 88-year-old Ethel since her husband died, but "she long ago stopped listening to or reading them. She tried to block them out then, too, although they must have hurt."
Amid the gossip, Tye said Ethel never wavered in solidarity with her husband: "She never disclosed any suspicions. What she knew then and still does is that she loved her husband more completely than she'd dreamed possible. And she knew he always came home, not just to the kids but to her."