Jackie Kennedy was aware that her letters to Irish priest Fr Joseph Leonard had been kept by the All Hallows Seminary in Dublin after his death in 1964.
She discovered, by chance, through separate correspondence she had with former Fine Gael taoiseach John A Costello in 1966, that Fr Leonard had "saved his letters".
The letters were sent over a 14-year period after she met the priest when visiting Ireland as a student in 1950.
The former US first lady did not seek either the return of the letters or their destruction.
However, she did ask if it would be possible for her to get copies to recall “so many things I had forgotten” and also “for my children one day”. She said she had kept “all” of Fr Leonard’s letters to her and “would love to match them up side by side” to show her children.
The Irish Times has learned that Mr Costello, who was also a friend of Fr Leonard's, facilitated this request. Copies were sent to her in New York in 1967.
She told her daughter Caroline, then aged 10, about her friendship with Fr Leonard and read extracts to her from one of the letters. Jackie was “so happy to see the effect on her – hearing how much she was loved and how much she was like her father”.
Her daughter made no attempt to recover the letters from All Hallows after Jackie’s death in 1994.
It has also emerged that Jackie was “deeply moved” that the seminary was looking after the letters and offered to bequeath to All Hallows the letters that Fr Leonard had written to her.
The revelations cast new light on the controversy surrounding the fate of the archive of letters which had been consigned to auction by All Hallows College last month.
The letters were withdrawn and returned to representatives of All Hallows and the Vincentian Order, of which Fr Leonard had been a member.
It is believed Caroline Kennedy, US ambassador to Japan, and her husband Edwin Schlossberg, have retained a Dublin law firm to assert their copyright of the content of the letters. The Vincentian Order has declined to comment on its plan for the letters.