Until recently, the final resting place of Indigenous soldier and WWI prisoner of war Robert George Garner was an unmarked section of grass, nestled between two concrete slabs in an unassuming corner of Sydney's Rookwood Cemetery.

But Garner's service to his country has been recognised at last, with his grave receiving a new commemorative plot and headstone.

Funded by the Department of Veterans Affairs, the new plot was visited by Garner's daughter, Fae Warry, for the first time.

She said her first visit to Rookwood in October 2015 had been the end of a lengthy search to find her father's grave that had brought feelings of guilt and sadness.

"It was an unmarked grave — it was just a patch of grass, so that was a bit sad, but we did have a couple of roses that we bought from the kiosk that we were able to put there," Ms Warry said.

"It was a terrible war and he must have went through hell, like they all did, so it's good to think that he is now being recognised like a lot of others are now being as well."

Photo found by Belgian collector

Garner's life was one of struggle, adversity and triumph — from his birth in Sydney's Benevolent Asylum to the bullet-riddled plains of the Western Front and the confines of German prisoner-of-war camps.

It was a story of great intrigue but one that few outside his immediate family knew.

That was until a photograph of Garner taken inside a POW camp in 1917 emerged online, sparking renewed interest in his life and a desire to appropriately acknowledge and recognise his military service.

The photo was from an album found by Belgian WWI collector and researcher Ian Roofthooft as he scrolled through online auction websites in early 2015.

Mr Roofthooft said he was caught off guard by the level of detail in the photos.

The album belonged to French soldier Emile Lansberg (back left), pictured here with fellow inmates. ( Supplied: Ian Roofthooft )

"There were photographs with soldiers, most French, but also Irish, Scottish, Belgian and Australian, and almost every photograph with a single portrait ... has the soldier's name and sometimes the address on the back," he said.

The image of the 26-year-old Garner, with his strong jawline, high cheekbones, tight curly hair and dark complexion, demanded attention, Mr Roofthooft added.

"A picture of an Anzac soldier in these camps is very rare, but a picture with an Aboriginal solider, it's almost impossible to find.

"So I was very surprised that there was a picture of this man in that album. He looked very good.

"On the back of the photo was his name and the village where he lived, and we soon found out he still had family in Australia."

Life as a POW

Michael Bell, the Indigenous liaison officer at the Australian War Memorial, said the discovery came as a welcome surprise.

"It's a stunning photo; he is a very good-looking, handsome, dignified man," he said.

Garner went missing in action in 1917 following a German attack against the 17th Battalion that resulted in heavy casualties.

His legs had been wounded by shrapnel and he received treatment at the Wahn POW camp.

In the months that followed, Garner was relocated to several camps across Germany including Hameln, Rennbahn (Münster II), Minden and Friedrichsfeld.

Robert George Garner (bottom right) with fellow inmates of the Friedrichsfeld POW camp in 1917. ( Supplied: Sunday Times )

Most prisoners were forced to provide labour for their captors six days a week, Mr Bell said.

"Robert George Garner is fairly unique for us: he is one of the 20 known Aboriginal prisoners of war in WWI."

Mr Roofthooft said the album he discovered belonged to a French soldier, Emile Lansberg, who had spent considerable time alongside Garner in the prison camps.

"It was not unusual that prisoners of war exchanged photographs of themselves as a souvenir of the war," he said.

After the war, Lansberg and his album returned to France, where it remained in his family until his grandchildren listed it for sale almost a century later.

Brothers in arms

Elias McAllaster followed his brother to the Western Front. ( Supplied )

Inspired by his older sibling, Garner's 19-year-old brother Elias McAllaster joined him on the Western Front.

Questions were likely raised as to both brothers' eligibility to serve, due to a policy at the time that restricted those of a non-European background from enlisting.

But exceptions were often made, Mr Bell said.

"It varied from doctor to doctor. Some would say, 'you're fine, you're healthy, you're fit, in you go', despite the colour of your skin, while others flatly refused."

McAllaster, a frontline trooper, took part in several significant actions, including the Battle of Bullecourt.

On May 3, 1917, he was wounded in action and left unconscious by an exploding shell.

He would complain of noises in his head, giddiness and difficulty standing, with a tremor throughout his body keeping him hospitalised for two months.

Failure to fully recover ultimately led to his military discharge.

Ms Warry was quite young when her father died, meaning most of what she knows about his life was told to her by her mother and older siblings.

Fae Warry at her father's grave, with its new plot and headstone. ( Supplied: Roy Warry )

She did, however, spend a considerable amount of time with her Uncle Elias, even living with the family during her teenage years.

She could not recall her uncle ever showing signs of physical or emotional struggle, though the same could not be said of her father.

"Uncle Eli seemed quite strong and well, but my father, he had problems — he had both legs injured from the war and he also had difficulty breathing."

While McAllaster lived into his 60s, Garner died aged 46 after long struggles with his health.

He spent the latter part of his life working as a labourer, supplementing his income by busking in the streets of Newcastle — Hawaiian music was a favourite.