The fiery accident killed Sheri and Jeffrey Cole and their four-year-old daughter, Grace. The couple's unborn child also died.
An Ogle County coroner's jury ruled Thursday that their deaths were homicides.
Authorities say Rodrigo Duran of Rochelle was traveling more than 100 miles per hour when he crashed his SUV head-on into the family's vehicle. The jury ruled Duran's death accidental.
The accident's only survivor was three-year-old Allison Cole, who remains hospitalized. Officials say she's showing small signs of improvement.