Tripplehorn, who is best-known for her roles in "Big Love," "Sliding Doors" and "Basic Instinct," joins a cast that already includes Jessica Lange and Drew Barrymore as eccentric members of the Kennedy family who lived in squalor in an East Hampton, N.Y. mansion, the Hollywood Reporter said Tuesday.
The new film was inspired by a 1975 documentary by the same name.
Also hired to act in the drama are Daniel Baldwin, Ken Howard and Malcolm Gets, the entertainment trade paper said.
The film is currently shooting in Toronto.
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