Police were alerted when a 25-year-old man, the eldest of the six children, visited a pub close to the family’s home in Ruinerworld.
The man was reportedly unkempt and unshaven and told the landlord he hadn’t been outside for nine years, TRV Drenthe reported.
He added he had brothers and sisters living on a farm and he wanted to change how they lived.
It’s believed the family had grown their own vegetables and drank goat milk, and were living in the bunker to survive the end of the world.
The landlord called police who found five other young people, the youngest being 16, and a 58-year-old man who was arrested for not cooperating with officers.
The basement’s entrance was reportedly hidden behind a cupboard.
It was initially reported that the older man was the children’s father and that he was bed-bound after a stroke, but the relationship has not been confirmed.
Neighbours told media they believed a single man lived at the property, while a local postman said he had never delivered mail to the farmhouse.