One of the surviving children of Sarah Barrass and Brandon Machin fears they could go on to kill "because that's what mum and Brandon did".
Barrass and Machin, who is her half-brother, strangled Tristan and Blake Barrass, aged 13 and 14, in May.
The pair were jailed at Sheffield Crown Court for a minimum of 35 years.
They had both previously admitted murder, conspiracy to murder all six of their children, and five counts of attempted murder.
All the surviving children, who cannot be named for legal reasons, are under the age of 13.
The court heard the children wanted their parents, from Shiregreen in Sheffield, to go to prison for "300 years".
The two older, surviving children - one of whom they tried to drown in a bath - have been left "emotionally broken" by the actions of their parents, jurors heard.
In a victim impact statement, the court was told one of them feared becoming a murderer.
Kama Melly QC, prosecuting, told the court: "When (the older two children) were told Sarah and Brandon had pleaded guilty to the murders of their brothers and the attempted murders of them, (one of them) said they were worried they would become a murderer when they were older because that's what their mum and Brandon did.
"They said they didn't want to be like that."
The court also heard the children did not know Machin was their father and had been told their father was dead.
Miss Melly said: "Both (the older children) are emotionally broken and don't know why this happened. They repeatedly ask why and how. We don't have the answers."
"Both keep saying they just want a nice family home and say they want their brothers back because it's too hard without them," she added.
The court heard the two youngest children, who are under age three, never asked for their mother or Machin, even when they were upset.
"There's no doubt that all four children will need ongoing psychological support," Miss Melly added.
She said the older two were "really struggling knowing they will not see their big brothers again and not seeing (their other siblings) every day.
"They have lost everything," the barrister added.
Jailing the parents at Sheffield Crown Court on Tuesday, Mr Justice Goss said: "Both the children who survived were clearly aware of some of the terrifying events surrounding the deaths of their brothers and your attempt to drown one of them."
"The initial effect on them, as described by them, was frightening. Unsurprisingly they are extremely upset and anxious," he added.
"The statement from their social worker on their behalf describes their inevitable confusion, the effect of the loss of their brothers upon them and the incredible emotional hardship of these events on (the older children) and of being separated.
"Inevitably they will require a significant amount of support. The long-term consequences for them and (the younger children) as they grow older and become aware of what happened cannot be known, but is likely to be significant."