A NSW teacher told by a pupil “My sister is pregnant and we don’t know which of my brothers is the father,” has led to a raid on a family farm.

This disturbing comment was made by a student at a southern NSW high school and sparked police intervention after the teacher informed the authorities.

The details were revealed yesterday in Sydney’s Parramatta Local Court as two members of the extended family living on the farm were ordered to have DNA tests, according to reports by the Daily Telegraph.

The isolated farm was raided in mid-2012 by police and child protection workers, who found a group of 38 adults and children living in filthy caravans and tin sheds without electricity, running water or any plumbing.

They were the result of four generations from grandparents who were brother and sister.

Twelve children ranging in age from five to 16 were removed from the farm, according to reports.

Police continue to investigate the family, known by the pseudonym Colt, for charges of rape and sexual assaults.

The court was told that 29-year-old Tammy Colt, a pseudonym for the sister referenced in the school conversation, gave birth to a baby who died within two months from a fatal genetic disorder known as Zellweger Syndrome.

Genetic tests confirmed the disease existed as a result of incest.

The father was not named on the birth certificate but Tammy reportedly has since told counsellors she had been having a relationship with a younger brother for three years.

Sally’s mother Betty Colt appeared yesterday in Moss Vale Local Court where her case was adjourned until August 18.