A mother who murdered two of her sons and plotted to kill four more out of fear they would be taken into care has been jailed for at least 35 years.
Sarah Barrass, 35, plotted with Brandon Machin, 39, to kill their six children in May.
Teenagers Tristan, 13, and Blake Barrass, 14, died after being strangled by the pair at a property in the Shiregreen area of Sheffield, and having bin bags placed over their heads.
Sheffield Crown Court heard on November 12 how, prior to the killings, Barrass and Machin had given four of their children - including Tristan and Blake - tablets against their will.
The pair also tried to kill one of their children by attempting to drown them in a bath.
Legal restrictions initially prevented the reporting of the relationship between the couple, but it has now been revealed that Machin is Barrass's half-brother and the father of the six children.
A judge ruled Barrass and Machin should both be jailed for life, with a minimum term of 35 years.
Prosecutors told how Barrass had requested help with the children from the local authority with the children, texting a friend to say: "I've thought of every possible solution to this mess. Mass murder, putting them all in care, checking in to the local nut house.
"I love my kids too much to kill them, I can't put them into care for the same reason."
Kama Melly QC, prosecuting, said that visitors to the children's home would hear Barrass tell her children: "I gave you life, I can take it away."
The pair forced four of the children to take what they expected to be a lethal quantity of tablets, including prescribed ADHD medication.
When the children survived, they strangled Tristan, 13, and Blake, 14, before trying to drown one of the younger children in the bath.
They hatched the plan after fears that the children were going to be taken into care.
Mr Justice Goss said to Barrass: "You considered your love for them and fear of being parted from them entitled you to take their lives as well as your own."
Miss Melly said that on May 23 this year, the two defendants gathered up tablets from around Barrass's home and divided them among the four eldest children, expecting them to die.
The barrister said: "None of the children wanted to take the tablets but were forced to do so."
The court heard Barrass sent messages and made social media postings overnight claiming that the youngsters were suffering from a sickness bug.
But when she realised that the tablets had not had the effect she wanted, she began to search for information on the internet about alternative methods of murdering her children, including suffocating, strangulation and drowning.
She then called Machin to tell him that their sick plot had failed, the court heard.
Miss Melly went on: "They decided the children were better off dead than in care and he said he would help Sarah Barrass to the best of his ability.
"Barrass and Machin first strangled Blake, then Tristan, then placed bin bags over their heads to ensure their certain death."
The court heard Barrass had strangled Tristan by wrapping her dressing gown cord around his neck and pulling on it for around three minutes, while Machin strangled Blake with his hands.
Following the murders and the attempted murder of the younger child who was placed in a bath, the mother took the surviving children, who are all under the age of 13, to the bedroom and phoned the police.
Her defence, Bryan Cox QC, said Barrass was "profoundly damaged by her childhood". The court heard she told police she planned to kill the younger two children and herself after the older four had died.
She described how the children were "terrified" as she tried to make them take the tablets and the child she tried to drown was "hysterical".
A serious case review will now be held into the deaths of the two teenagers.
John Macilwraith, executive director of people services at Sheffield City Council, said: "The sentencing of Sarah Barrass and Brandon Machin for the double murder of Tristan and Blake Barrass has today concluded the legal process. Our focus continues to be the wellbeing of the children from this family now in our care. They are safe and receiving good support through this traumatic time.
“The Sheffield Children Safeguarding Partnership has initiated a Serious Case Review (SCR) to investigate what happened. The national SCR panel have endorsed this and agreed that the review should go ahead locally. The council will be cooperating fully with the review and are already working to provide the relevant information. This is such a tragic and, we hope, isolated case that it is vital to examine every aspect in order to establish what can be learned to inform the development of future professional practice.
“We anticipate that the SCR will take up to six months, but this is subject to many factors and timescales may change. The most important thing is taking the necessary time to get the review right.
“We have many hundreds of families in Sheffield who are cared for by our children’s services but there are always new lessons to learn, so we need to understand, alongside all partners in the city, as much as we can about why and how these tragic events happened, as much as it is ever possible to understand such a terrible act.”