The cruel parents subjected the youngsters to years of abuse, including pressing hot spoons on their skin, holding knives to their necks, beating them with belt buckles and coat hangers, making their daughter sleep in a tent for three weeks after she wet the bed, and stabbing her with a dirty needle and telling her she would die of Aids.
After a week-long trial, the parents have finally been brought to justice and a judge has told them they are facing a jail sentence.
Preston Crown Court heard that the couple hid their crimes by lying to social services and 'brainwashing' their daughter and two sons into believing their sadistic punishments were 'horseplay'.
The mother, a care-home worker, boasted to a friend that she headbutted the children and once hit them so hard that she burst a blood vessel in her hand.
Despite complaints to social services and the children's school by a family friend 'every week', the youngsters remained in their parents' care in Chorley, Lancashire, until the eldest approached the police.
Judge Pamela Badley said: "This is a very distressing case, and one where your heart went out to the children whose bitterness while giving evidence was quite palpable.
"The children have clearly been brainwashed and each parent seemed to have their own agenda, blaming each other and saying they were manipulated by the other into carrying out the abuse. The defendants are clearly going to be facing custodial sentences."
The parents, who cannot be named for legal reasons, were convicted of four counts of child cruelty, having previously admitted five similar offences. They will be sentenced next year, and could face a maximum prison sentence of 10 years each.