The Dutch family found "waiting for the end of the world" at a remote farmhouse in Ruinerwold once had ties to the Moon cult, according to local media.
In an interview with De Telegraaf, a relative of the mysterious family-of-six said the father, Gerrit-Jan, was once part of the Unification Church, a powerful South Korean religious movement known for its mass weddings.
"Gerrit-Jan broke with the rest of the family a long time ago," the 32-year-old cousin said.
"About thirty years ago anyway. There was a lot of disagreement between my parents and my uncle, and between my uncle and the church association. At a certain moment he ran away angry. That was before I was born."
Gerrit-Jan's eldest son, 25-year-old Jan Zon van Dorsten, raised the alarm about his family's living conditions when he fled from the farmhouse on Sunday to a nearby pub.
He ordered and drank five beers before telling the owner he feared for his family's safety and didn't want to go home.
That led police to an isolated farm where they found Jan's ailing father and his four other children aged between 18 and 25 hidden in a secret room.
Josef B, the 58-year-old Austrian handyman who rented the farm, was arrested by police and charged with unlawful detention and harming others' health, news.com.au reported.
Neighbours described him as a "sharp" character who was very protective of his home, while his brother told the Austrian newspaper Kronen Zeitung he had also been involved in a cult.
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According to Franz B, who said he hadn't seen his brother in years, Josef had joined a "sect" while enrolled in the army and behaved as though he was "better than Jesus".
On Thursday, a Dutch court extended Josef's detention for at least another two weeks.
WHAT IS THE UNIFICATION CHURCH?
The Unification Church was founded in 1954 by South Korean pastor Sun Myung Moon, a self-proclaimed messiah who believed he was chosen by Jesus to continue his work bringing peace to the world.
The church has millions of followers around the world, often referred to as 'Moonies', but very few in the Netherlands.
The movement is famous for its mass weddings – sometimes involving more than 2,500 people – which Moon would personally officiate until his death in 2012.
But critics have warned it's a dangerous cult with powerful business interests, especially in the United States where it owns the daily Washington Times newspaper.
In 1984, Moon was jailed in New York for tax evasion.