Safety warnings about Arthur Labinjo-Hughes by his family and neighbours were ignored, his grandfather has said.
Peter Halcrow, the boy’s maternal grandfather, claimed that warnings from other family members were “not acted on” by police or social services.
On Friday, she was sentenced to life imprisonment for his murder. His father, Thomas Hughes, 29, was sentenced to 21 years for manslaughter.
Speaking to BBC Radio 4’s Today programme, Mr Halcrow said that warnings had been issued by the boy’s other grandparents.
“They’re decent people and they were very concerned,” he said. “And they issued warnings that were ignored, shall we say.”
He went on to claim that West Midlands Police had been called about the situation but the force had not stepped in.
As for the couple responsible for his death, Mr Halcrow said they had committed a “heinous crime” by killing a “defenceless, innocent boy”.
He added: “I wouldn’t give them the time of day and I wouldn’t want them to see the light of day ever again.”
Solihull’s Local Child Safeguarding Partnership launched an independent review after it emerged in court the boy had been seen by social workers just two months before his death, but they concluded there were “no safeguarding concerns”.
Education secretary Nadhim Zahawi on Monday announced a national investigation would commence into what went wrong in the lead up to Arthur’s death.
He told the House of Commons: “I am as determined as everybody in this House to get to the truth and expose what went wrong, and take any action necessary to protect children.”
A separate review will also take place examining the sentencing of Arthur’s killers, and will be carried out by the Attorney General’s Office (AGO).
The AGO has 28 days from the date of sentence to review a case, assess whether it falls under the Unduly Lenient Sentence (ULS) scheme, and make a decision as to whether to refer a sentence to the Court of Appeal.
The Evening Standard has contacted West Midlands Police for comment.