John F. Kennedy had an affair with a 19-year-old intern while he was president, the author of a new biography said this week. She had no skills, Robert Dallek, author of An Unfinished Life, said on Dateline NBC, other than the apparent capacity to provide sexual release for J.F.K. A former reporter who once spotted the young woman sneaking up to Kennedys hotel suite described her as a colt, young and very trim. The tale merely added to Kennedys reputation as a philanderer. The late president has been romantically linked to a string of women, including Marilyn Monroe and a pair of presidential aides known around the Kennedy White House as Fiddle and Faddle.