They were lured away by the brothers, who promised they would show them a toad they had found, but instead they were subjected to a horrific assault.
Jenny Hill, BBC News, Sheffield Crown Court
The crimes that these brothers committed, the injuries they inflicted, were considered so severe that they were initially charged with attempted murder.
They pleaded not guilty to attempted murder but guilty to a lesser charge, grievous bodily harm.
The court has accepted that lesser charge.
The Crown Prosecution Service and South Yorkshire Police said they believe this is the right decision because of course it stops the victims having to relive the traumatic attack during a trial which would have taken certainly two or three weeks.
The decision was taken in accordance with the families of those victims, who say they are particularly relieved that the boys would not have to relive what had happened to them.
The maximum sentence for grievous bodily harm is the same as the maximum sentence for attempted murder, so the feeling here at the court is very much that the difference in charges really doesn't actually affect the outcome of this.
The older boy had a sink dropped on his head, one had a noose put around his head and one was burned with a cigarette on his eyelids and ear.
The younger boy had a sharp stick rammed into his arm and cigarettes pushed into the wound.
He also tried to ram a stick down his own throat after he was told to "go away and kill himself" by one of his attackers.
The pair, who were both seriously injured, had bricks thrown at them and were repeatedly stamped on.
The nine-year-old managed to stagger to a nearby house to raise the alarm, covered in blood from wounds to his head and arm.
The 11-year-old boy was later discovered unconscious in the nearby wood.
The brothers have each pleaded guilty to robbing one of the boys of a mobile phone and the other of cash.
They also admitted two counts of intentionally causing a child to engage in sexual activity.
The brothers were later charged with attempted grievous bodily harm with intent and making a threat to kill in connection with a separate attack on another 11-year-old boy in Doncaster a week earlier.
The pair had denied these offences, but each have pleaded guilty to a lesser charge of assault occasioning actual bodily harm.
The court heard the brothers picked a "discreet" location for the scene of their first attack, in trees by a stream.
I'm gonna die, I'm gonna die - that's what I kept repeating in my head
Victim of first attack
But they were interrupted by a passer-by.
The victim of that attack said: "They got me into these bushes, and then the fat one punched me.
"They stamped on my head. After, like, twenty minutes of them hurting me, this man came and said 'Oi, what you doing?'... and they said 'You've got twenty seconds to run' so I ran as fast as my little legs could carry me.
"I'm gonna die, I'm gonna die. That's what I kept repeating in my head."
A week later the brothers chose a "more isolated" place for the attack on the two boys.
The boys were led to a large mound of timber, described as a "den", which was hidden from public view, where some of their injuries were inflicted.
The brothers then moved their victims to a second site, at the foot of a 15ft ravine. It was here that a broken sink was used to inflict the more serious head injuries on the 11-year-old.
Brothers admit attack on two boys
Det Supt Mick Mason said the victims suffered a "traumatic experience" but were "recovering well".
"The victims are still suffering, certainly mentally, and also recovering from the physical wounds," he said.
The mother of the eldest victim said she was "pleased" with the guilty pleas.
She said the families were not upset about the decision to accept pleas to lesser charges and she was happy the boys did not have to be put through a trial.
Nicholas Campbell QC, prosecuting, described the offences as "grave crimes".
The prosecutor said on the day of the second attack, the two brothers should have been at the police station being questioned about the earlier assault.
He said: "Instead, they went out and attacked [the two boys]."
The Crown Prosecution Service (CPS) said the decision not to pursue the attempted murder charges was taken in consultation with the victims' families.
Doncaster Council said a serious case review was now under way to establish if there are lessons to be learned by any agency involved.
The judge, Mr Justice Keith, will visit the site of the attacks before the boys are sentenced.
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