Six years after stories of alleged neglect, incest and paedophilia on a NSW farm shocked the world, eight members of the infamous "Colt" clan have been arrested at remote properties in three states.

The family matriarch, Betty Colt, was flown into Sydney on Friday evening after NSW Police successfully sought the extradition of all six interstate suspects.

They were arrested on Thursday at the same time as a man and a woman were nabbed in Griffith, in the NSW Riverina region.

About 40 members of the clan were discovered living in squalor on a rural property near Yass in 2012.

The children had speech difficulties, bad hygiene, slept in tents and later told caseworkers they had had sex with their siblings and relatives, including brothers and uncles, a NSW court would later hear.

Genetic testing suggested 11 of the 12 children, aged between five and 15, had parents who were related.

Family members were given pseudonyms by the courts including the surname "Colt" as the children were taken into state care.

Since then detectives have amassed DNA, forensic and witness evidence that led to the Colt inner circle being charged on Thursday.

Police footage of the NSW arrests shows officers handcuffing the diminutive Charlie Colt wearing high-vis workwear next to a tractor.

He kneels in the red Riverina dirt - still holding a cigarette - while a detective stands over him scribbling in a notepad.

The 45-year-old was charged with more than a dozen offences, including six counts of sexual intercourse with a child under 10.

Martha Colt, 38, is shown being escorted to Griffith Police Station with her hands in her pockets. She was charged with perjury.

The pair appeared in Griffith Local Court on Friday and were refused bail.

They are due to appear in a Sydney court on Thursday.

Meanwhile, a man and two women were arrested in the Riverland region of South Australia on a NSW warrant.

Derek Colt, 29, faces two charges of incest with a person under the age of 16 while Raylene Colt, 34, and 50-year-old Betty face perjury charges.

Two men and another woman were also arrested in the Northam area of Western Australia.

The six interstate accused are expected to appear at Parramatta Local Court on Saturday.

The NSW child abuse squad chief on Friday told reporters the investigation had "tested the resilience" of detectives as they waded through the accusations of "horrific" abuse.

The Colt family originated in New Zealand with Tim and June marrying in the mid-1960s before emigrating to Australia. Betty is believed to be their child.

The clan spread to remote parts of Australia after the NSW farm was raided in 2012. Detectives on Friday wouldn't confirm if any of the removed children had since returned.

AAP understands clam members have continued to reproduce - but none of the pregnancies resulted in surviving children.