The 48-year-old woman, Betty Colt - a pseudonym assigned for legal reasons - was also found guilty of procuring a child to commit the crime of kidnapping.

The offence carries a jail sentence of up to 15 years, though in a magistrate's court the maximum available sentence is two years.

Magistrate Mary Ryan said Colt had deliberately tried to induce her two children, who were in care in the Southern Highlands, to run away when the oldest, Bobby (also a pseudonym), turned 16.

Ms Ryan said the evidence given by Bobby revealed an "overbearing , immature and claustrophobic" relationship between Colt and her sons. "As a mother, she showed an inability to put the children's interests first," she said.

The magistrate said the Children's Court had awarded care to the minister until the children turned 18 because of the "appalling" conditions they had been found in. She also noted that the Children's Court said Colt was aware of  the incest and consanguinity issues that had impacted on not just her own generation, but the next generation as well.

During their time in care, the boys had received therapy and treatment for dental and eye conditions, she said.

Ms Ryan said Colt understood the boys could not leave until they were 18 but she had been intent on taking them to South Australia. She had secretly given Bobby a mobile phone and made hundreds of calls to the children, many of which were intercepted by police.

Even though the plot did not proceed - police arrived to intercept the runaways and arrested Colt - Ms Ryan said: "I have no doubt that Bobby would have coerced Billy [also a pseudonym] to leave, not through force but through the force of personality of their mother."

The magistrate noted that the older boy suffered from delayed development and the younger was moderately intellectually impaired.

The prosecution alleged she was intent on reclaiming the children to prevent them being questioned about allegations of incest and child abuse on a remote farm in southern NSW, near Canberra.

Five of Colt's 13 children were removed into the care of the state in 2012, after they were found living among a group of 40 adults and children on the isolated farm.

Another seven children under the age of 16 also living on the squalid farm were removed.

The children were undernourished and had severe dental problems. Some were unable to talk intelligibly and were well behind their peers developmentally, while some have intellectual disabilities. The farm had no running water or toilets and some of the inhabitants were living in tents.

Once in care, the children, who were aged from five to 15 years old, gave carers horrific accounts of being sexually abused by their siblings and by adults on the farm.

Subsequent genetic testing has revealed that of the 12 children under the age of 16 who were removed, 11 had parents who were related. Colt was living in an incestuous relationship with her brother on the farm.

In September last year, the Children's Court ordered the children be placed in permanent foster care until they turn 18.

In doing so, the judge, Peter Johnstone, said the case appeared to involve "intergenerational incest" as there was evidence that the four mothers had themselves been the victims of sexual abuse within the family from as young as 12.

The family moved from interstate to NSW in 2009, but Fairfax Media understands the family may have already come to the attention of child protection services in other states and moved to avoid orders relating to their children.

The magistrate has asked for a sentencing report ahead of a further hearing on November 3.

Detective Inspector Peter Yeomans of the Child Abuse Squad said police were pleased with the result.

"We are only partially through our investigation of these matters," he said. "Without our intervention, these children would have been taken out of care and returned to a life of abuse and neglect."