Hamzah Khan's body was found in an insect-infested baby-gro, intended for a baby aged six to nine months, when police made the discovery in September 2011.
The four-year-old had died 21 months earlier, on December 15 2009.
Following the conviction of Amanda Hutton, questions are raised over two little boys killed by those who were supposed to care for them.
A mother who starved her son to death threatened to kill her other children, a judge who sentenced her to 15 years in prison heard.
For two years the mummified body of four-year-old Hamzah Khan lay hidden in his mother's squalid house.