Daniel Pelka was murdered by his stepfather and mother in Coventry.
The man convicted of murdering a four-year-old boy in Coventry has been found dead in jail.
Mariusz Krezolek, 36, was found dead in his cells by guards at about 08:30 GMT on 27 January at Full Sutton prison.
He was sentenced to a minimum of 30 years in jail in 2013 after being convicted of murdering his step-son, four-year-old Daniel Pelka.
Daniel’s mother, Magdalena Luczak, who was also convicted over his death, was found hanged in her cell in July 2015.
Latest updates on this story
A spokesman for the prison service said Krezolek was found “unresponsive” in his cell, and despite efforts to revive him he was pronounced dead shortly afterwards.
“As with all deaths in custody, there will be an investigation by the independent Prisons and Probation Ombudsman,” they said.
Daniel was starved and beaten for months before he died from a head injury in March 2012 at his Coventry home.
During the trial of Krezolek and Luczak Birmingham Crown Court heard he weighed just over a stone and a half when he died.
He was denied food, poisoned with salt, locked in a small room, forced to perform punishment exercises and subjected to water torture.
Daniel had been treated at hospital for a broken arm, and turned up at school with bruises and facial injuries.
A teaching assistant had said he looked like “a bag of bones”, and he had been seen scavenging for food.
Judge Mrs Justice Cox said Daniel’s mother and step-father had acted with “incomprehensible brutality” towards him, causing the toddler “severe physical and mental suffering”.
Mariusz Krezolek (left) and Magdalena Luczak both died in prison after their convictions