BORN. To Diana, Princess of Wales, 23, and her husband Charles, Prince of Wales, 35, heir to the British throne: their second child, a boy; in the same private suite in London's St. Mary's Hospital in which their son Prince William was born in June 1982, with the Prince in attendance, and heralded by a 41-gun salute from troops in Hyde Park and by the cheers of crowds that had stood outside the hospital since the Princess's arrival early in the morning. Weight: 6 Ibs. 14 oz. The newest Prince is third in the line of royal succession, after his father and brother.

MARRIED. Nastassja Kinski, 23, German-Polish film star (The Hotel New Hampshire, Maria's Lovers); and Ibrahim Moussa, 37, Egyptian-born international representative of Rome's Bulgari jewelry firm and the father of her 2 1/2-month-old son Aljosha; both for the first time; in New York City.

JAILED. Dennis Banks, 53, a Chippewa Indian and co-founder of the militant American Indian Movement, who was convicted of assault and rioting in connection with the February 1973 burning of the Custer, S. Dak., courthouse, but who fled sentencing in 1975 and has lived in sanctuary for the past nine years on Indian reservations in California and New York State; in Rapid City, S. Dak., where he turned himself in and was denied bail. Banks will be sentenced on Oct. 8 and faces a maximum of 15 years in prison.

HOSPITALIZED. Barbara Mandrell, 35, bouncy blond country-music queen; for surgery to repair a broken leg and lacerated knee received when her Jaguar was hit head-on in Hendersonville, Tenn., by another car (its driver was killed); in Nashville. She and her two children, ages 14 and 8, were apparently saved by seat belts, which the three had buckled up moments before the crash. The accident will put her concert-touring career on hold for at least four months.

DIED. Yilmaz Gueney, 47, acclaimed fugitive Turkish film maker who wrote and supervised the direction of the movie Yol (The Road) while serving a 19-year prison sentence in Turkey for murder, but who escaped to edit the film and see it share top honors at the 1982 Cannes Film Festival; of cancer; in Paris.

DIED. J. Robert Fluor, 62, California conservative who helped build his family's Irvine-based engineering and construction company into one of the nation's largest, and who backed Republican and pro-business candidates and causes with his and his company's considerable resources ($27.7 million profits on $5.3 billion in revenues in fiscal 1983); of cancer; in Corona Del Mar, Calif.

DIED. Janet Gaynor, 77, diminutive red-haired movie actress of the 1920s and '30s, who won the first Academy Award for Best Actress in 1929 for her leading roles in three films, Seventh Heaven, Sunrise and Street Angel; of pneumonia and the cumulative effects of injuries she received in an auto accident in San Francisco two years ago, in which her husband Producer Paul Gregory and Actress Mary Martin were also hurt; in Palm Springs, Calif. After a twelve-year career, during which she was a top box-office attraction in such films as State Fair, The Farmer Takes a Wife and A Star Is Born, she retired from the screen in 1939 to marry Dress Designer Gilbert Adrian; until his death in 1959, the couple spent most of their time on a Brazilian ranch. Occasionally emerging from retirement for film, stage and TV roles, she married Gregory in 1964; they lived on a ranch near Desert Palm Springs. Of her Life, she once said: "Most people stress the unhappiness in their careers. I had a glorious twelve years in mine, as strange as it seems."

DIED. Horace Jerry Voorhis, 83, respected former Liberal Democratic Congressman from California whose ten-year political career was abruptly ended in 1946 by a novice Republican named Richard Nixon, after a bruising campaign during which Nixon repeatedly accused passionate New Dealer Voorhis of being soft on Communism; of emphysema; in Claremont, Calif. Voorhis spent the next 20 years as executive director of the Cooperative League of the U.S.A. and never again ran for public office.