The CW has announced details of a prequel to its longest-running show Supernatural centred around the Winchester brothers' parents.

The drama, starring Jensen Ackles and Jared Padalecki, came to an end last year after a landmark 15 seasons on the air.

The Winchesters will aim to tell the story of the boys' parents, John and Mary Winchester, and how they got into the business of demon hunting.

Ackles will return as narrator of the new show and will also serve as executive producer alongside his wife Daneel Ackles.

"After Supernatural wrapped its 15th season, we knew it wasn't over. Because like we say in the show, 'nothing ever really ends, does it?'" Ackles told Deadline.

"When Danneel and I formed Chaos Machine Productions, we knew the first story we wanted to tell was the story of John and Mary Winchester, or rather the Supernatural origin story.

"I always felt like my character, Dean, would have wanted to know more about his parents' relationship and how it came to be. So I love the thought of having him take us on this journey."

The Winchesters has yet to get an official pickup to series although The CW has committed to a script order.