http://assets.nydailynews.com/img/2009/12/29/alg_yacht_john-f-kennedy.jpg Throughout his presidency and his marriage to Jackie Kennedy, JFK was known as a playboy. But stories about his swinging lifestyle, including his alleged affair with Marilyn Monroe, have mostly been hearsay. Four decades after his death, TMZ has obtained a photograph that forensic experts suggest may prove President John F. Kennedy's libidinous appetite.