They found the women – aged 55 and 77 – living in reclusive squalor, the house dilapidated and home to dozens of cats, a few raccoons and an opossum.

That was intriguing and peculiar enough, except that the women were Edith Ewing Bouvier Beale, born in 1895 and known as Big Edie, and her daughter, Edith Bouvier Beale, born in 1917 and known as Little Edie.

And they were the aunt and cousin of Jacqueline Bouvier Kennedy Onassis.

The filmmakers, brothers Albert and David Maysles, filmed the pair talking about their lives, singing songs and showing the two rooms they now lived in. Their once beautiful 28-room shingle-style house, a block from the sea in the US's wealthiest beach town East Hampton, was an overgrown shambles.

The footage was later confiscated by Onassis' sister Lee Radziwill​ who had taken the Maysles there with the idea they make a film about her and her sister's childhood.

But the Maysles returned, gaining permission to film again and paying the Beales $5000 each. The result was the 1975 documentary Grey Gardens, a landmark work of cinema verite.

Little Edie Bouvier Beale in a still from the documentary Grey Gardens by Albert and David Maysles.

Even before the original documentary came out, the world had already been alerted to the Beales' lives. A National Enquirer story and a New York magazine cover by Gail Sheehy sparked a nationwide scandal after they detailed the filthy, rat-infested, rubbish-strewn living conditions of the former First Lady's reclusive relations.

Inspectors from the Suffolk County Health Department reportedly found a 1.5-metre-high pile of empty cans in the dining room and human waste in the pair's shared bedroom.

County officials said Grey Gardens, built in 1897, broke every known building regulation, but the Beales were outraged.

"We're artists against the bureaucrats," Little Edie said. "Mother's French operetta. I dance, I write poetry, I sketch. But that doesn't mean we're crazy."

To avoid their eviction, Onassis and Radziwill donated $30,000 for basic repairs.

The money soon ran out, allowing the house's condition to deteriorate again, but the impoverished pair refused to leave. They existed, in part, on boiled corn, liver pate and crackers. Albert Maysles (David died in 1987, Albert in January) said they spent $150 a month on ice-cream. 

Scene from the documentary film The Beales of Grey Gardens by David and Albert Maysles.

​The documentary made the Beales cult figures and, unexpectedly, fashion icons.

It is a story of broken dreams and a daughter held relative captor by her mother, two extraordinary characters and their loving but embittered relationship.

They were "staunch" women, as Little Edie says to David Maysles' camera.

"S-T-A-U-N-C-H," she spells out, dressed in a buttoned-up trench and pale blue towel head scarf adorned with an elaborate brooch. "There's nothing worse, I'm telling you. They don't weaken, no matter what."

Little Edie had a gilded youth, living a life of privilege until her father left her mother and paid only child support for her and her two brothers. She modelled successfully and wanted to be a dancer and actress.

She lived in Manhattan at the Barbizon Hotel for Women for five years in her quest to break into showbusiness. But in 1952, aged 35, she relinquished her artistic dreams and any romantic attachments to live with, and care for, her ailing, penniless mother.

Big Edie was cut out of the family will after she attended her son's wedding dressed as an opera singer.

Little Edie, once a tall, blue-eyed blonde beauty who dated Howard Hughes and reportedly received proposals from Joe Kennedy jnr  and J. Paul Getty, was a witty, limelight-loving card. She danced, sang, sashayed and flirted for the Maysles' camera.

She also concocted memorably improvised outfits out of swimsuits (she swam in the sea regularly), cardigans safety-pinned to become skirts and beautiful, elaborately pinned fabrics to become dresses. And always a headscarf, said to cover a bald head caused either by alopecia or Little Edie setting her hair on fire in a rebellious act while up a tree.

The Sydney premiere of Grey Gardens, the musical, is the work of Squabbalogic​ theatre company.

Director Jay James-Moody says he was drawn to the production because of the ingenious portraits of the Beales through its music and lyrics.

"I knew exactly who these women were through the songs," he says. "And I think Little Edie would be happy and amazed that their story has gone so far. I believe she knew that the musical was happening and for her to become this fashion icon, she would have been so excited and thrilled.

"What I find so incredible is that they were not ashamed or self-conscious about their lives or who they were. They seriously maintained their dignity throughout."

James-Moody recently visited Grey Gardens, in its restored glory. It is now available to rent for holidays (the June and July rental price was $125,000) and he walked through the beautiful rooms and gardens with goosebumps tingling the back of his neck.

"I went in every room but I cannot remember one thing about Little Edie and Big Edie's bedroom. It is so famous. I stood in it but it has just left my mind."

When Big Edie died in 1977, Onassis and Radziwill attended the funeral. Little Edie inherited the house but was otherwise destitute, and sold it in 1979.

Big Edie and Little Edie in their bedroom in a scene from the documentary Grey Gardens.

The new owners were writer Sally Quinn and her husband, the late Ben Bradlee, executive editor of The Washington Post. They bought Grey Gardens with all its contents (including silver and china, photographs, letters, scrapbooks and Louis Vuitton trunks) for $220,000 (A$171,000).

Under Quinn's direction and Little Edie's blessing, the house was restored to its original condition and it became their family holiday home. It is now worth $US20 million ($28 million) but Bradlee was initially doubtful.

"I wasn't sure I wanted to buy the house," he told The New York Times. "There were 52 dead cats in it, and funeral arrangements had to be made for each one."

In a 2013 interview before Bradlee died, Quinn said the house still smells like cat urine by the front door when it rains.

"Ben always takes people over to the corner and makes them get down on their knees and smell the floor," she said.

In 1978, Little Edie made her New York stage debut at the age of 60 in a Greenwich Village club, Reno Sweeney. She performed eight shows, singing songs by Cole Porter and Noel Coward, and featured in a question and answer session ("What is your favourite department store?" "Mays!" "What do you think of television?" "It's very good for national emergencies." "What's your opinion of premarital sex?" "I think it's very economical.")

The reviews were bad but the club owners ensured she never saw them.

Little Edie's fashion nous became influential. She met Andy Warhol and Gianni Versace, and designer Marc Jacobs created the "Little Edie" bag.

Her last residence was in Florida, where her modest Miami Beach apartment had views of palm trees and sailboats. She swam in the ocean every day.

"I only cared about three things: the Catholic church, swimming and dancing, and I had to give them up," she says in Grey Gardens. But in the end she had her own share of fame. In the 2002 Academy Awards montage remembering film luminaries who had died, Little Edie's portrait was included.

At 84, in 2002, she was found dead at home from a presumed heart attack. She had not owned a cat for five years.

Grey Gardens plays at the Seymour Centre, Chippendale, from November 18.