The Welsh woman knew her paternal grandfather was Australian and had fathered a son in England before he apparently disappeared from history in February 1920.

But beyond that, for 30 years, he's been little more than a name.

Now living in Ruthin, North Wales, Mrs Cooper and her granddaughter Rebecca Bloomfield have pieced together the mystery, connecting the enigmatic figure with another long-held family mystery from Junee.

They were not, in fact, the only people in the world searching for any clue of what happened to the missing man.

The first breakthrough came when the Welsh family detectives discovered that the name O'Brien had been an alias. His original name was Breen.

That was all former Junee resident Michele Koulouris needed to know to begin unravelling the century-old mystery.

"I saw a post on Junee Remembers [Facebook page], Rebecca had posted looking for any Breens in Junee," Ms Koulouris said.

"My mother was a Breen. Her father was the brother of Michael. She always spoke about Michael and how they couldn't find him. Up until the day he died, my mother's father didn't know where he was."

During the post-World War I era, his family had spent years hoping that he would return, or at least that word would be sent of his whereabouts.

"Every time there was a sighting they'd send someone to look for him, they even paid people to try and find him," Ms Koulouris said.

In 1920, his parents in Junee had received a telegram from the lieutenant indicating that he was soon to return to his family home. But years went by and he did not appear.

"They had been worried that he was mentally injured in the war, that he couldn't get back," Ms Koulouris said.

Born on April 4, 1894, in Tarlo near Goulburn, Michael was one of nine children. With parents Mary Agnes Drew and John Michael Breen, the family had moved to Junee when Michael was very young.

John Breen would later re-marry a woman named Kathleen, who became the mother of Winifred Breen, Ms Koulouris's mother.

When he enlisted for World War I, Michael Breen changed his name to O'Brien.

His papers indicate he crossed out the name of John Breen of Fairlight, Junee as his next of kin, writing over it with the name Elsie Henry.

Though efforts were made after the war to send his personal effects on to her, the address he had given was "Wagga Wagga" and it prevented her from ever being found.

"Neither our family nor the Breen family knows why Michael enlisted under a false name, or why he didn't put a family member down as a next of kin," Ms Bloomfield said.

He joined his brother, William, on the battlefield. One died, the other vanished.

Though there is no known grave for the late Private William Breen of Millbank, Junee, his military service records indicate he died at Polygon Wood, Belgium in 1917. He was only 27 years old.

"My mum always felt like it was her duty to find out where [Michael] went," Ms Koulouris said.

After contacting the family in Wales, Ms Koulouris and her 86-year-old mother Winifred agreed to take a DNA test. It confirmed the lineage.

"Mum got her results back, it matched with Gail," Ms Koulouris said. "She [mum] has lost so many family members, it's lovely to have just found more."

Living on the Northern Beaches and unaware of his namesake, 66-year-old Michael 'Micky' Breen was alerted to the story by a text message.

"My cousin messaged me with some of the info the Welsh family had found. I did a DNA test," Mr Breen said.

"I uploaded the results to GEDmatch and it matched to them in Wales. My aunt was a second cousin, [Michael] was my father's uncle. I might even be named after the missing Michael."

Now knowing some of the history, Mr Breen intends to go further, retracing his family's arrival in Australia.

"John Breen came out as a convict, his grave is on a property near Goulburn which is where he settled," Mr Breen said.

"His daughter is also buried there. There's actually a lot of connections to the Breens. There's a Breen Road in Canowindra, there's a Breen Street [in Lavington]. The Breens have been there for centuries."

He now plans to take his 29-year-old son, Dominic, to explore their ancestral lands.

"I drove back from Canberra not too long ago, and it's funny before knowing this I've always felt an affinity with that area," Mr Breen said.

The military kept letters from Dennis Breen, Michael's brother, inquiring of his whereabouts. The last correspondence dates to August 1919.

Other family members, including step-niece Myrtle May Woods and sister-in-law Mrs N Breen, wrote to desperately find him, but to no avail.

"The Breen family were under the impression that Michael would be returning on one of the last boats of men returning to Australia after the war," Ms Bloomfield said. "The Breens continued to search for Michael for the rest of their lives."

A letter from an Angus Byron Craft of Wagga remains a mystery. It requests information on the whereabouts of both Michael Joseph O'Brien and Michael Breen, originally leading the family in Wales to believe they were two separate people.

Angus Craft made efforts to contact Elsie Henry in Wagga but reveals he could not track her down.

"We have not been able to find or confirm exactly who Angus or Elsie were, or what their relationship was to Michael," Ms Bloomfield said.

Though Michael O'Brien never seemed to have reconciled back to his family in Junee, a family reunion is taking shape among the next generations.

"We are so excited and happy to have found Michael's real birth family, and to be in contact with so many of them," Ms Bloomfield said.

"They are truly wonderful people. To their knowledge, Michael's family were not aware that Michael had had a son in England."

While the mystery is now partially solved, Michael O'Brien's descendants continue to have a few questions yet to be answered.

"Why did he change his name? What happened to him after he left his family [in 1920] and who was Elsie Henry?" Ms Koulouris asked.

"To let his family go on not knowing where he'd gone, that must have been torturous. He caused so much heartbreak."

The journey through history began with a box of photographs uncovered in England three decades ago.

Now, the family in Wales will continue to unravel the strands of secrecy surrounding the elusive Michael Joseph O'Brien, until they uncover every mystery he held in the annals of time.

"Despite Michael's interesting story, our family have nothing but pride and love for Michael," Ms Bloomfield said.

"There are no ill feelings towards him, we just want answers and closure.

"What happened to our Australian war hero grandfather?"

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