A woman broke down in tears as she was told she could spend the rest of her life in prison after admitting murdering her two teenage sons while conspiring to kill four more of her children.

Sarah Barrass, 35, pleaded guilty to the murder of Tristan Barrass, 13, and Blake Barrass, 14.

The brothers died in hospital 12 minutes apart after police were called to the Shiregreen area of Sheffield, South Yorkshire, at about 7.30am on 24 May.

Postmortems have been carried out but the results were not given during a hearing on Friday at Sheffield crown court. The exact circumstances surrounding the boys’ deaths are not yet known.

Barrass appeared in the dock alongside her co-defendant, Brandon Machin, 39, a family member. Flanked by three security officers, they pleaded guilty to two counts of murder and one count of conspiracy to murder six children.

The pair also pleaded guilty to five counts of attempted murder during the 20-minute hearing. The conspiracy to murder charges relate to a period between 14 and 20 May .

Four of the attempted murder charges relate to four children, including Blake and Tristan on 23 May. The fifth count of attempted murder took place on 24 May. The surviving children are all under the age of 13.

The judge, Jeremy Richardson QC, told the pair: “No words of mine can ever fully reflect the enormity of what you have both done. The crimes you have committed quite frankly speak for themselves. The murder of two children. The attempted murder of four children and the overarching conspiracy to murder those children.

“I have little doubt that each of you will in due course be sentenced to several terms of life imprisonment. It’s a matter for the judge where a whole life order is imposed.”

They will be sentenced on 12 November.