The eldest of two Ontario siblings who went missing overnight, prompting an Amber Alert, kept calm and looked after his five-year-old brother, their mother said on Friday.

Ten-year-old Tyson Fildey and his brother Mason Fildey-Holyj, 5, were found about three kilometres north of their home in Springwater Township, near Barrie, Ont., on Friday morning.

"I was so happy. I just ran down here to see them," said Elizabeth Fidley, their older cousin, adding they looked scared.

The boys had gone missing more than 12 hours earlier, after disappearing while playing outside their home Thursday night.

"I'm very proud of Tyson that he took care of his little brother," mother Jennifer Fildey told reporters. "They just decided to stay in a spot and sleep, and hope that they would be found in the morning."

Jennifer was worried about a nearby river, fearing the boys could have fallen in.

The boys were taken to a hospital in nearby Collingwood, Ont. as a precaution. Tyson and Mason were found to be in fine shape, just a little cold and exhausted after their overnight ordeal.

"My feet were getting really cold. We were just trying to find somewhere to stop," Tyson said Friday afternoon. "It was getting dark. I knew where we were -- I just didn't want to walk home in the dark."

Tyson said the pair had simply been out playing. When it got too dark to find their way home, they hunkered down in a ditch.

Tyson made the decision to go home in the morning, "and we're going to make it through the night," he said.

Overnight lows dipped to -3C in the area. Tyson wrapped one coat around Mason's cold feet and used his own jacket as a blanket.

Ontario Provincial Police had issued an Amber Alert -- in part because of reports of a suspicious truck in the area -- and launched a search team that included marine, canine and helicopter units.

The alert was lifted shortly after 7 a.m., when a township employee on regular patrol spotted the pair on the side of a rural road.

The sound of police cars and helicopters woke them up, Tyson said.

Ontario Provincial Police Const. Peter Leon says the boys appeared little worse for wear after their overnight adventure.

"They looked cold; there was no doubt about that. They had a little bit of dirt and mud on them from their ordeal. But I would suggest that Tyson, the older boy, definitely looked out for his younger brother," Leon told CTV News Channel.

Leon said the boys' safe recovery elicited a great sense of relief among the family and those involved in the search.

Two years ago, another Barrie-area case did not have a happy ending.

Brandon Crisp, 15, went missing on Thanksgiving Day 2008, leaving home after an argument with his parents about his video-game obsession. Hunters found his body at the base of a tree off a trail east of Barrie several weeks later.

With a report from CTV Toronto's Austin Delaney