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Rose Marie "Rosemary" Kennedy (September 13, 1918 - January 7, 2005) was the oldest daughter born to Joseph P. Kennedy Sr. and Rose Fitzgerald Kennedy, and was a sister of President John F. Kennedy, and Senators Robert F. Kennedy and Ted Kennedy. Rosemary experienced mental disabilities, and displayed less academic and sporting potential than her siblings; however, her disabilities were carefully concealed from the public by her prominent family. In her early young adult years, she also had behavioral problems. Her father arranged one of the first prefrontal lobotomies for her at the age of 23, but it failed and left her permanently incapacitated.

Kennedy was presented to King George VI and Queen Elizabeth during her father's service as the United States Ambassador to the United Kingdom. Her father presented his daughters instead of, more customarily, choosing about thirty young American debutantes, a decision which earned him favor in the press. Kennedy's "slowness" was also unconventional and daring for a debut (two of the queen's nieces remained in a mental hospital because they were mentally ill). Young women would practice the rather complicated royal curtsey, sometimes learning the performance at the Vacani School of Dancing near Harrods. She practiced for hours. She wore a gown made of white tulle with a net train and carried a bouquet of lilies of the valley. Her sister Kathleen was described as "stunning, but she was only a shadow of Rosemary's beauty." Just as Rosemary was about to "glide off" by stepping to the right, she tripped and nearly fell. Rose Kennedy never discussed the incident and treated the debut as a triumph. The crowd made no sign, the King and the Queen smiled as if nothing had happened, and it is unknown whether Rosemary was aware of her own stumble.  One Kennedy family biographer termed her "absolutely beautiful" with "a gorgeous smile." At twenty, she was "a picturesque young woman, a snow princess with flush cheeks, gleaming smile, plump figure, and a sweetly ingratiating manner to almost everyone she met." She enjoyed dancing, such as at her sister Kathleen's coming-out party. Kennedy's parents told Woman's Day that she was "studying to be a kindergarten teacher," and Parents was told that while she had "an interest in social welfare work, she is said to harbor a secret longing to go on the stage." The Boston Globe wrote requesting an interview which was refused, but her father's assistant Eddie Moore prepared a response, which Rosemary copied out laboriously, letter by letter:  I have always had serious tastes and understand life is not given us just for enjoyment. For some time past, I have been studying the well known psychological method of Dr. Maria Montessori and I got my degree in teaching last year.
Rosemary Kennedy