The mother of five-year-old Logan Mwangi and two others have been found guilty of his murder.
Angharad Williamson, 30, her partner, John Cole, 40, and a youth, 14, have all been convicted of the same offence.
The little boy had 56 external injuries when he was found in a South Wales river last July.
Weeks before he died, he suffered a broken collarbone but was not taken for treatment.
All three defendants were also accused of perverting the course of justice, something Williamson and the youth were convicted of.
Cole, who was captured on CCTV carrying Logan’s body to the River Ogmore while being followed by the teenager, admitted the charge.
The youth, who did not give evidence, had earlier been heard singing: "I love kids, I f****** love kids, I love to punch kids in the head, it’s orgasmic."
Logan’s father, Ben Mwangi, was in court for the verdicts, during which Williamson screamed "no, no, no" from the dock as they were returned.
Judge Mrs Justice Jefford interrupted the jury and the clerk to tell Williamson to be quiet before the verdict against the youth was given.
"Out of respect for your son and the youth please be quiet for the verdicts," she said.
She told the jury they had performed an "exceptional public service" while listening, at times, to "very unpleasant and emotional evidence".
Speaking outside Cardiff Crown Court afterwards, Mr Mwangi said Logan was the "most beautiful boy" and the world is a "colder and darker place without his smile and happy energy in which he lived his life".
He added: "I loved him so much and somehow I have to live my life knowing I will never get to see him grow up."
The child, also known as Logan Williamson, was found dumped in the river near his home village of Sarn in Bridgend on 31 July last year.
He was wearing mismatched pyjamas and was said to have undergone a "brutal and sustained assault".
His injuries were described as similar to victims of high-speed crashes or someone who had fallen from a height.
When he died, he had been isolating for 10 days after testing positive for COVID-19 and was treated like a "prisoner", the prosecution said.
Detective Inspector Lianne Rees, senior investigating officer in the case, said the defendants’ "callousness and lack of remorse" were shown by their "attempts to cover up the crime and the subsequent web of lies and deceit that were to follow".
Doctors made a safeguarding referral to police after Logan suffered a broken arm in August 2020. Williamson said he had fallen down the stairs.
Later, she told a friend the youth had confessed to pushing Logan down the stairs but it was not until January last year that she told the police.
By March, because of concerns about Cole, Logan and a younger sibling had been assigned their own social worker, Gaynor Rush.
But in June, the month before Logan died, the family were removed from the child protection register.
NSPCC Cymru has called for a child safeguarding practice review.
Its assistant director, Tracey Holdsworth, said Logan’s treatment was "horrific, but for his death to have involved another young person is even more shocking".
She added: "We cannot lose sight of the fact that one of those found guilty is still a child and the response to him must be one of both punishment and appropriate support.
"A Child Safeguarding Practice Review must now leave no stone unturned in establishing exactly what took place before Logan died and whether more could have been done to protect him."
Mrs Justice Jefford adjourned the case for sentencing at a date to be determined.
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