Thousands of pages of files released Monday by the FBI reveal numerous threats against the late Sen. Edward Kennedy and also enhance the myth of the three young Kennedy brothers, whose status as American royalty in the 1960s was cemented through hard political work — and what seems to be even harder play.

The 2,234 pages of files on the Massachusetts Democrat concern mostly threats of violence or extortion against the Senator, some from groups such as the mafia, the Ku Klux Klan, Minutemen organizations and the National Socialist White People’s Party.

But there are also salacious allegations that Kennedy, along with his brothers — President John F. Kennedy and then-Attorney General Robert F. Kennedy — engaged in wild sex parties in the early ’60s with the likes of Frank Sinatra and Marilyn Monroe.

The files also include correspondence between Kennedy and then-FBI Director J. Edgar Hoover, detail accounts of Kennedy’s trips overseas and provide limited details on Edward Kennedy’s 1969 car accident on Chappaquiddick Island, which resulted in the death of a young campaign aide, Mary Jo Kopechne.