"They're very cold." Children find parents dead after they didn't wake them up for school.

When Brian Halye, 36, and his 34-year-old wife Courtney failed to wake up their children for school last Thursday, their kids sensed something was wrong.

The couple’s four children – aged between 9 and 13 – went to find their parents, and found them overdosed on the bedroom floor of their Ohio home.

"My two parents, I just woke up, and my parents are on the floor," the pair's 13-year-old son told dispatchers after phoning 911.

"My sister said they are not waking up. They’re not breathing...They were very cold."

The boy also said his parents were very pale, and his dad had "black lines" on his face, but that his parents had seemed "fine" the night before.

In a separate phone call to 911, the boy's sister said her mum and stepdad were "on the floor".

"They're not waking up...we just woke up for school," she said.

Preliminary examinations revealed the couple likely accidentally overdosed on fentanyl and/or heroin, Montgomery County Coroner’s Office Director Ken Betz told Dayton Daily News.

A final determination on the couple's cause of death may take up to six weeks.

Mr Halye was a pilot working for commercial airline Spirit Airlines.

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The company confirmed he had been flying with the airline for just over nine years, and completed his last flight on March 10.

"Our hearts go out to the family, friends and colleagues of Captain Hayle," Paul Berry, the company's spokesman said.

Family members have revealed that Ms Halye had long battled with drug dependency.

Her former husband, Jacob Castor, died in August 2007 from an accidental drug overdose, the Dayton Daily News reports.

In reports obtained by news site WHIO, Courtney's mother, Nancy, contacted police in January 2016 and said she felt her daughter was "abusing narcotics" and had "threatened to harm herself".

In the report, she said her daughter had been "hooked on drugs" on and off for about seven years.

The same report revealed Ms Halye's husband had phoned police after she refused to answer calls and tell him where she was.

When he later found her at their home, Mr Halye forced himself into the property as he believed Ms Halye had access to two guns he kept in the house.

When police arrived, he had just taken the guns from her.