Jackie Kennedy’s affectionate letter to husband JFK offers a rare peak into their marriage

A love letter that Jackie Kennedy wrote to John F. Kennedy offers us a rare glimpse inside their "atypical" relationship.

The three-page love letter, which was written in either 1957 or 1968, has been put up for auction.

According to an online listing by RR Auction, Jackie wrote, “I can’t help it if when I go away from you I write stiff letters.”

“It is hard for me to communicate — which you do so beautifully — and it just seems easier to write you facts than all the strange things that go through my mind.”

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She proceeded with, “I know everyone says married couples shall never separate — as you get off the same wave length — it is true you do — but I think it is usually good when we go away from each other as we both realize so much.”

Jackie, who became the first lady after JFK was sworn in as president in 1961, wrote that she and her better half were “so different.”

"But I was thinking this trip—that every other time I've been away, you would write 'don't ponder our relation too much" etc.—and now I don't as one doesn't ponder anything that is a part of you," she added.

The socialite is open with JFK about the fact that their marriage may not be what both of them anticipated.

“You are an atypical husband — increasingly so in one way or another every year since we’ve been married — so you mustn’t be surprised to have an atypical wife,” Jackie wrote.

“Each of us would have been so lonely with the normal kind. I can’t write down what I feel for you, but I will show you when I am with you — and I think you must know."

Jackie also wrote about their daughter, Caroline. "It must be 5 years and at least a baby we both love," she expressed.

“All my love, Jackie," she signed.

This letter has an expected worth of more than $20,000. RR Auction wrote in the description that it is the only one “ever offered at auction.”

Jackie's world collapsed when JFK was assassinated on November 22, 1963. He was 46.

The former First Lady was married to her second husband, Aristotle Onassis, from 1968 until his death in 1975. She passed away at age 64 in 1994.

Jackie was a fashion icon. Her iconic ensemble of pink Chanel suit and matching pillbox hat has become a symbol of JFK's assassination.