The teen, who was 13 at the time of the deaths, was arrested last week for killing 23-month-old Desiree McCartney in May 2017.
He also stands accused of killing 11-month-old stepbrother, Nathaniel Ritz, at their home in Osgood, Indianapolis.
“He’s not the monster that people are trying to portray him as,” his mother, Christina McCartney, told reporters.
“It’s a mother’s worst nightmare to have such a precious family and then to wake up to the worst possible outcomes.”
He told police that he killed them so that they wouldn’t “have to live in the hell that he did” and to save them “from hell and the chains of fire”.
When questioned what that “hell” was, the boy reportedly replied “chores,” before asking officers if they’d seen the list of daily chores he had to complete.
The judge is yet to rule on whether the teen is competent to stand trial, and whether or not to grant prosecutors’ request that he be tried as an adult.