A court heard the young victims were subjected to horrific physical and mental cruelty by the mother who ignored the sexual abuse carried out on them by her husband and son.
Leeds Crown Court heard the vulnerable youngsters were subjected to abuse over a ten-year period at their home in west Leeds.
Jailing them to a total of 29 years, judge Sally Cahill, QC, said: “It is difficult to find to words to describe you.
“You are each guilty of the most enormous breach of trust and the depths of your depravity is almost breath taking.
“You are in my view some of the worst examples of humanity.”
The court heard the victims endured “the childhood from hell”.
One of the girls was forced to suffer regular physical assaults by the mother and was left permanently scarred after one attack.
Attacks included her being punched and dragged around by her hair or ears. On another occasion she was thrown out into the street and had to spend the night outside alone.
She was regularly humiliated by the mother. On one occasion she was forced to eat birthday cake until she was physically sick.
During a trial the victim recalled how she was made to write out text from thick books and would have to start again if she made a mistake.
Locks and alarms were placed on all the doors of the property to prevent the girls moving about the house.
They were often sent to their rooms as punishment, where the light bulb would be removed and windows would be taped up to block out the light.
The father and son were found guilty of carrying out various sex offences which were ignored by the mother.
When teachers became concerned for one of the girls and police and social services became involved she was told she would be “battered” if she said anything to them.
Whenever she complained about the sex attacks she was called a “slag” and a “prostitute” by her mother and was not believed.
Judge Cahill told the mother: “You were trusted by society to take those girls and care for them with the love and guidance to which all children are entitled.
“Instead you gave them what can only be described as the childhood from hell.
“Rather than give them the love of a mother, you treated her in a way in which....she was absolutely terrified of you.
“You caused her physical scars but the emotional scars go even deeper. You were supposed to be the mother and instead you were the abuser.
“In my view you are almost as equally responsible as your husband.”
To the father she said: “”This was the most massive breach of trust. You were entrusted with a child who you adopted and she was entitled to believe you would care for her as any father should. But you used her for your own purposes over a long period of time.”
The son, who carried out the sexual offences when he was around 15 or 16, was told: “You took advantage of a younger and vulnerable sister. You knew how your mother treated her.”
The father was jailed for 12 years after being found guilty of attempted rape, two offences of sexual activity with a child, two of sexual assault and three of indecent assault.
The mother was jailed for nine years after pleading guilty to three offences of cruelty.
The son was jailed for eight years after being found guilty of three offences of rape.
After the case, Jane Held, chair of the Leeds Safeguarding Children Board said:
“These were despicable crimes against two vulnerable children. It is only right that the perpetrators of this terrible abuse have been convicted of their crimes.
“All agencies in Leeds responsible for safeguarding children take crime of this nature very seriously and this case illustrates the lengths to which some peretrators will go to access children. It is important that all agencies responsible for safeguarding children are vigilant and that children have access to trusted adults to whom they can tell their story to and who will listen to them and act. Here in Leeds we have specially trained social workers who are able to support children who have experienced this sort of abuse.”