Mariusz Krezolek was serving a life sentence for his role in the death of the four-year-old, who was starved and beaten.
16:15, UK, Friday 29 January 2016
The killer of schoolboy Daniel Pelka has been found dead in prison, months after his partner was found hanged in her cell.
A judge said the four-year-old was the victim of an "incomprehensible cycle of cruelty and violence" which left him looking like "a concentration camp victim" before he died of a head injury in 2012.
Krezolek was discovered unresponsive in his cell at HMP Full Sutton in Yorkshire on Wednesday morning.
A Prisons Service spokeswoman said: "Staff immediately attempted resuscitation but he was pronounced dead shortly after."
Luczak, 29, was found dead at HMP Foston Hall in Derbyshire in July last year - two years into her sentence.
He weighed just 1st 9lb when he died.
The medical evidence, the judge said, showed that Daniel's emaciation was regarded by experts as "unprecedented" in Britain.