Five-year-old Logan Mwangi's voice was not heard by authorities during his short life, a review detailing the extensive injuries he suffered has found.
Thirty-one images were taken of injuries, during a health assessment undertaken by a paediatric doctor in August 2020, a review commissioned by the Cwm Taf Morgannwg Safeguarding Board said.
The injuries included a 1cm blue mark above the child's penis.
Logan's mother Angharad Williamson told the Health Board she did not know how the mark had occurred.
Other injuries included bruises to the boy's ankle, forehead, ears, arm, cheeks and a carpet bruise to his chin.
Williamson said Logan would bang his head, pinch himself and that the mark to his ears was from a mask.
The little boy was present during the discussion between his mother and a health worker, the review stated.
He said he had fallen down the stairs and agreed when his mother gave the cause of the bruising to his ears as being from a mask worn due to the pandemic.
He also stated that he banged his head and pinched himself when he got angry.
The review concluded that there was no evidence that information about the injuries recorded by the doctor was shared with agencies outside of the Health Board.
The board, which published its review on Thursday, said there had been an absence of one-to-one sessions with Logan outside of his family home.
The review said this was due in part to restrictions during the pandemic, as well as "resulting pressures upon child protection systems at that time, such as high levels of staff absences" due to Covid 19.
The review stated that Logan's "voice was not heard" and that "the complexities of the adult relationships" involved in his care "overshadowed professionals' line of sight to him".
"There was no knowledge of the reality of his lived experience," it added.
The review stated that there had been a failure to share some of Logan's injuries with "services that could have taken appropriate action to safeguard him".
It said several injuries, even in isolation, "should have triggered" a child protection referral.
Weeks before he died in July 2021, Logan suffered a broken collarbone but he never got medical treatment, the trial of his killers heard.
As she sentenced Logan's mother Angharad Williamson, his stepfather John Cole and his stepbrother 14-year-old Craig Mulligan earlier this year, Mrs Justice Jefford said Logan had been subjected to a "brutal attack" before his death.
She told the trio: "Because he was killed in his own home and by his own family, it is not possible to be sure exactly what happened to him but what is very clear is that shortly before his death, this little boy - three feet and five inches in height and weighing only three stone and one pound - was subjected to a brutal attack."
She said the injuries suffered by Logan were the "sort of injuries seen in abused children".
"The inflicting of these injuries on a small, defenceless five-year-old is nothing short of horrifying," she added.