Question: The Parent Trap originally starred which younger sister of Juliet Mills?

Context articles: The Parent Trap II
Hallie Meyers-Shyer
Parent Trap: Hawaiian Honeymoon
Carrie Kei Heim
Sir John Mills' Moving Memories
The Parent Trap (1961 film)
The Parent Trap (film series)
The Parent Trap (song)
Hayley Mills
Parent Trap III

The Parent Trap II is a 1986 American made-for-television comedy film and a sequel to Disney's 1961 classic "The Parent Trap" and the second installment in "The Parent Trap" series.
 It premiered on Disney Channel on July 26, 1986 as a part of the channel's "Sunday Night Movie".
Hallie Meyers-Shyer (born July 26, 1987, in Los Angeles, California) is an American film actress, director and writer.
 She is the youngest daughter of writer/directors Nancy Meyers and Charles Shyer, and has appeared in six of her parents' films: "Father of the Bride", "I Love Trouble", "Father of the Bride Part II", "The Parent Trap", "What Women Want", and "The Affair of the Necklace".
 Her older sister Annie has also made film appearances; the twin characters in "The Parent Trap" were named after Hallie and Annie.
Parent Trap: Hawaiian Honeymoon is a 1989 American made-for-television comedy film and a sequel to "Parent Trap III" (1989) and the fourth and final installment in "The Parent Trap" series.
 It originally aired in two parts on "The Magical World of Disney" on November 19 and 26, 1989.
Carrie Kei Heim (born December 7, 1973) is an American actress, lawyer, and writer.
 She is best known for her roles as Cornelia in "" and Nikki Ferris in "The Parent Trap II".
 After completing "The Parent Trap ll", Carrie retired from acting.
Sir John Mills' Moving Memories is a British documentary film featuring 16mm color home movies shot by the actor Sir John Mills.
 It documents his life between 1946 and 1969, directed and edited by Marcus Dillistone and produced by his son Jonathan Mills.
 Commentary was provided by Sir John (who was over 90 years old at the time), Hayley Mills, Juliet Mills and Sir Richard Attenborough.
 His wife Mary Hayley Bell is also seen towards the end of the film listening to her husband singing at the piano.
 The scene was later to be screened in full when Sir John appeared on the Parkinson show.
The Parent Trap is a 1961 Walt Disney Technicolor film.
 It stars Hayley Mills, Maureen O'Hara and Brian Keith in a story about teenage twins on a quest to reunite their divorced parents.
 The screenplay by the film's director David Swift was based upon the 1949 book "Lottie and Lisa" (German: "Das Doppelte Lottchen" ) by Erich Kästner.
 "The Parent Trap" was nominated for two Academy Awards, was broadcast on television, saw three television sequels, was remade in 1998 with Lindsay Lohan, and has been released on digital stereo LaserDisc format in 1986 as well as VHS and DVD in 2000.
 The original film was Mills' second of six films for Disney.
The Parent Trap is a film series, originating in 1961 with Hayley Mills as the twins.
 She reprised her role three times in made-for-television sequels; once in 1986 and twice in 1989.
"The Parent Trap" was the title song from the 1961 Disney film, "The Parent Trap".
 It was sung by teen idols, Annette Funicello and Tommy Sands and it was written by the songwriting brother team of Robert and Richard Sherman.
Hayley Catherine Rose Vivien Mills (born 18 April 1946) is an English actress.
 The daughter of Sir John Mills and Mary Hayley Bell, and younger sister of actress Juliet Mills, Mills began her acting career as a child and was hailed as a promising newcomer, winning the BAFTA Award for Most Promising Newcomer for her performance in the British crime drama film "Tiger Bay" (1959), the Academy Juvenile Award for Disney's "Pollyanna" (1960) and Golden Globe Award for New Star of the Year – Actress in 1961.
 During her early career, she appeared in six films for Walt Disney, including her dual role as twins Susan and Sharon in the Disney film "The Parent Trap" (1961).
 Her performance in "Whistle Down the Wind" (a 1961 adaptation of the novel written by her mother) saw Mills nominated for BAFTA Award for Best British Actress.
Parent Trap III is a 1989 American made-for-television comedy film and a sequel to "The Parent Trap II" (1986) and the third installment in "The Parent Trap" series.
 It originally aired in two parts on "The Magical World of Disney" on April 9 and 16, 1989.