A “Pretty Little Liars” alum is set to play a Kennedy in a new psychological thriller

Marina WattsMon, June 1, 2026 at 9:05 PM UTC

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Sasha Pieterse; Rosemary Kennedy
Credit: Paul Archuleta/Getty; George Rinhart/Corbis via GettyKey Points -

Rosemary Kennedy, JFK's sister, will be getting the biopic treatment with Pretty Little Liars alum Sasha Pieterse starring.

In 1941 at 23 years old, her father Joe Kennedy Sr. arranged for her to undergo a lobotomy, that left her incapacitated for the rest of her life.

Rosemary, who died in 2005 at 86, is the latest member of the political dynasty to have their life story dramatized.

Rosemary Kennedy is the latest member of the political dynasty to get the biopic treatment.

Pretty Little Liarsalum Sasha Pieterse's next role is playing the sister of President John F. Kennedy in the upcoming psychological thriller film Rosemary, Deadline reports. Rosemary was the third of Joe Kennedy Sr. and Rose Kennedy's nine children.

The film will “dramatize Rosemary Kennedy’s struggle with mental health, the devastating decision by her father, Joseph P. Kennedy Sr., to subject her to a lobotomy at age 23, and the long–lasting consequences of that choice," per Deadline. It will be based on the All That’s Interesting article titled "Rosemary Kennedy, JFK’s Sister Who Was Lobotomized And Locked Away."

Sasha Pieterse in New York in January 2026
Credit: Stephanie Augello/Variety via Getty

She reportedly had difficulty learning in school, along with experiencing developmental delays. As a young adult, it is believed that Rosemary exhibited violent mood swings during a time when mental health was stigmatized. However, she participated in many family activities and was even presented in court when Joe Kennedy was appointed the U.S. Ambassador to Britain.

Her sister Eunice wrote in her diaries, per the JFK Library and Museum, that “Rosemary was not making progress but seemed instead to be going backward.” Adding that “at 22, she was becoming increasingly irritable and difficult.”

In 1941, at 23 years old, her father arranged for her to undergo a lobotomy that left her incapacitated. After the new and risky procedure, she was no longer able to take care of herself. Rosemary was sent to St. Coletta’s School for Exceptional Children in Jefferson, Wis., where she lived for the rest of her life.

She was cut off from the family until 1961, when her father suffered a stroke. Rosemary's lobotomy was not made public until 1987, when Doris Kearns Goodwin wrote about the devastating procedure in The Fitzgeralds and the Kennedys.

Rosemary died of natural causes on Jan. 7, 2005, at 86.

Industry vet Mike Medavoy, known for his work on Black Swanand Shutter Island, will helm the project.

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“This film takes a story that has long lived in the shadows of history and places Rosemary at the center, not as a footnote in a political dynasty, but as a young woman with hopes, fears, and a voice that was never truly heard,” he said in a statement.

Pieterse told Deadline that Rosemary's multifaceted life attracted her to this role. “Rosemary’s story has been told in fragments. What drew me to this project is how it explores her as a person, not a symbol, but a fully realized human being with dreams and vulnerabilities," she said, per Deadline.

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Cory Todd Hughes and Adrian Speckert are slated to write and direct the upcoming film. They are known for the movies Under Fire and Foster.

“This isn’t just a historical biopic. It’s a psychological journey told through Rosemary’s eyes, one that challenges the audience to reckon with how we define agency, dignity, and identity," they said.

Rosemary Kennedy and Joe Kennedy Sr. in London in June 1938
Credit: Getty

Entertainment Weekly contacted reps for Pieterse, MOTUS Studios, and Phoenix Pictures.

This Kennedy-related project is the latest of dramatizations involving the political dynasty. Most recently, the FX series Love Story: John F. Kennedy Jr. and Carolyn Bessetteaired on FX, starring Paul Anthony Kelly and Sarah Pidgeon.

Currently in development is the Netflix series Kennedy, starring Michael Fassbender as the patriarch, Joe Kennedy Sr. In this dramatization, Rosemary will be played by Lydia Peckham and Tipper Seifert-Cleveland.

on Entertainment Weekly

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