Emma Stone has been tapped to play the mentally-disabled sister of US President John F Kennedy in a new film entitled Letters From Rosemary.

Stone will portray Rose Marie 'Rosemary' Kennedy, the eldest sister of the late president and senators Robert F Kennedy and Ted Kennedy.

The film will delve into Rosemary's ongoing behavioural problems and show signs of a mental disability which the iconic political American family kept secret.

At the age of 23, her father, Joseph Kennedy, Sr, arranged for her to receive one of the first prefrontal lobotomies to help cure her illness, but the procedure failed, leaving her permanently incapacitated.

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The movie will follow the events which led up to the life-changing surgery and how it affected the family moving forward.

Letters From Rosemary is written by new screenwriter Nick Yarborough, and his spec script for the biopic previously landed a coveted spot on Hollywood's Black List of unproduced screenplays.

- AAP