A 5-year-old Arizona boy died after being left inside a scorching hot car for hours while his family hosted a huge gathering … and now his parents are facing serious charges.

Theo Sabo was found unresponsive Sunday afternoon inside a vehicle outside his family’s Peoria home … where temperatures climbed to around 106 degrees.

Police say the family had returned home from another child’s baptism around 1 PM and was hosting a party with dozens of friends and relatives … but Theo apparently never made it inside.

More than two-and-a-half hours later, the family realized he was missing and found him in the vehicle. Relatives performed CPR before first responders rushed him to a hospital, where he was pronounced dead.

Theo’s parents, Mihail Sabo and Anca Sabo, were arrested and charged with negligent homicide and child abuse — they have four other children aged 18, 15, 14, and 9.

Here’s where things get even messier … Mihail allegedly told investigators he had asked the couple’s 14-year-old son to get Theo out of the car … but the teen told authorities he did not remember being asked to do that.

The family’s attorney is calling Theo’s death a heartbreaking accident, arguing there was a tragic miscommunication and the parents should not be treated like criminals.