Jordan Keely Arwood of Stanley cried during the hearing Thursday in Lincoln County and refused to talk to the media afterwards, the Gastonia Gazette reported.
"He's still minus two in his family. He'll have to live with that for the rest of his life," his lawyer, Brad Smith, said.
Chloe Arwood, 6, and her cousin, Jordan Caldwell, 7, were killed in April in a hole Arwood had been digging near his mother's home in western North Carolina. Arwood, who planned to build a house next to his mother, had been excavating for several months.
During Thursday's hearing, Arwood's mother, Nancy Caldwell, testified that her son did not allow the children to play in the excavation. Prosecutors produced a photo from his cell phone, taken a few weeks before the children died, that showed them in the hole.
On April 7, the children apparently slipped into the hole without anyone noticing. Caldwell said she heard screams.
Hundreds of emergency workers dug frantically, in an effort to rescue the cousins. Their bodies were discovered hours later.
Superior Court Judge Ali Paksoy agreed with Smith that the deaths were accidental.