Kathleen Joyce Heggs, 66, is set to appear in Dubbo Local Court on Wednesday on two counts of domestic violence murder.
Her grandsons Max and Sam Johnson, aged seven and six, were found dead in their home on the outskirts of Coonabarabran, in northwest NSW, on the afternoon of May 5.
Two junior police officers broke into the Emu Lane house after a message sent to the communities and justice department triggered an emergency response.
They found the boys' bodies in their bedrooms.
Heggs, their maternal grandmother, had harmed herself and was immediately arrested and taken to a mental health unit at Orange hospital.
She was the sole carer for the boys and the family had moved from the NSW Central Coast to the small rural town about a year ago.
Heggs has since been released from hospital and is on remand, a NSW Corrective Services spokeswoman confirmed.
NSW Police will apply to the court for permission to carry out a forensic procedure on Heggs as their investigations into the killings continue.
At Heggs' first court appearance, five days after her arrest, police documents alleged she may have killed the boys as early as 10.30am on May 5.
Police have previously said there were no weapons involved in the alleged murders.
The boys' deaths shook Coonabarabran, where they went to the local primary school and attended karate classes.
Community members held a candlelight vigil in a park by the Castlereagh River, where they planted two trees in the boys' honour and displayed the yellow karate belts they were due to receive.
Warrumbungle Shire Councillor Kodi Brady read a poem describing the boys as "wild as March hares, full of spark and flame".
"The town is hushed, the heart is torn, for two young lives, so dearly mourned," Mr Brady's poem said.
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