JFK's missing brain was stolen by Robert Kennedy after his assassination to stop it ever going on display, according to secret US government files.

Former US President Kennedy was murdered 55 years ago today but one of the greatest enigmas surrounding his death remains the location of his brain that mysteriously vanished.

The Sun reports that bombshell US Government documents actually back-up long-running claims that blame JFK's younger brother RFK for swiping the brain.

Files compiled by the House Select Committee on Assassinations, which probed JFK's murder, suggest the brain may have pinched to "prevent future display".

The document reads: "Circumstantial evidence tends to show that Robert Kennedy either destroyed these materials or otherwise rendered them inaccessible".

"It would seem to indicate that Robert Kennedy then decided to retain possession of all physical specimen evidence and transferred only the autopsy photographs and X-rays to the Government."

The whereabouts of JFK's brain have puzzled theorists for years after it was removed during the President's autopsy and later disappeared from the National Archives.

Conspiracists claimed the missing organ vanished to conceal evidence that Kennedy was not shot from the back by Lee Harvey Oswald, but from the front.

A 2013 book called End of Days: The Assassination of John F. Kennedy, first claimed that an inquiry ordered by then attorney-general, Ramsey Clark, indicated that RFK was the thief.

The latest US government documents incredibly seem to agree with this theory, noting RFK wanted to keep hold of the brain to prevent "public display".

US assistant Attorney-General Burke Marshall told the investigators: "Robert Kennedy obtained and disposed of these materials himself, without informing anyone else."

The report states Marshall added: ""(He) was concerned that these materials would be placed on public display and wished to dispose of them to eliminate such a possibility.

"(He) emphasised that he does not believe anyone other than Robert Kennedy would have known what happened to the materials and is certain that obtaining or locating these materials is no longer possible."

Robert Kennedy was killed on November 20, 1968, moments after winning the California primary in the race to become the Democratic candidate for the Presidency.

He was shot three times by Palestinian-born Sirhan Bishara Sirhan and died the following day after failing to regain consciousness.

The murders of both Kennedy brothers have been the subject of numerous conspiracy theories since their deaths.

This article originally appeared in The Sun and is republished here with permission