Letter Up for Auction From Robert Kennedy's Sister Says He and Marilyn Monroe Were an 'Item'

The letter from Jean Kennedy Smith was written to Marilyn Monroe in the 1960s.

Is there finally written proof that Robert Kennedy and Marilyn Monroe were paramours?

A letter for sale from Kennedy sister Jean Smith to the Hollywood sex siren contains the titillating line: “Understand that you and Bobby are the new item! We all think you should come with him when he comes back East!”

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The two-page missive was written in the 1960s, when Marilyn was often seen in the company of Peter Lawford, a Kennedy brother-in-law, and when she famously sang “Happy Birthday” to John F. Kennedy in a breathy voice and a barely there dress.

That flesh-colored, beaded gown also is part of the trove of Monroe personal items up for auction and it’s expected to fetch as much as $3 million at a Beverly Hills auction scheduled for November 17.

Rumors of alleged affairs between Monroe and both brothers have swirled for decades.

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The troubled actress died in 1962 from a drug overdose. JFK was assassinated a year later in Dallas and RFK met a similar fate in Los Angeles six years later.

Also up for bid: Her 1947 contract with Twentieth Century Fox, a recipe for stuffing, her final checkbook, a pair of strap sandals she wore in 1943 while still named Norma Jean, and a negligee from the movie “Niagara.”

The letter was discovered among papers Monroe left to her famous acting coach, Lee Strasberg. His son, David, found them packed into suitcases and cupboards while cleaning house.

Watch: Marilyn Monroe's Iconic Dress Worn For JFK's Birthday Could Fetch $3 Million at Auction