The discovery of a haunting letter, written to the mother of a young soldier killed on the Western Front on Anzac Day 90 years ago, has sparked a search for descendants. The typed letter from the trenches was found by former army captain Nick Lynch while clearing out his father's shed in Essendon, in Victoria. It had been neatly tucked behind a wartime photograph of Charles Alfred Porter Forster. Forster, from Gippsland, enlisted in Melbourne at the age of 19. He died just a year later in fearsome fighting at Villers-Bretonneux.

His troop sergeant, Alfred J. Parr, wrote to Forster's mother, describing her son's death and expressing his sympathy. He told how a German soldier had fired at him but missed, and "the bullet struck your son on the forehead and death was instantaneous". And he offered comfort: "Many times have I been comforted with the thought, though we mangle and maim and kill, yet we cannot destroy the beautiful soul that is in us, God's own image . . . God grant you strength, and to all 'mothers of men'."

Sgt Parr wrote that he'd seen "Oh! so much of this fearful carnage" and all had suffered, including his own mother, who "has given two" and anxiously awaited his return. She waited in vain. Not long after writing to the Forster family, Sgt Parr was also killed. He was awarded a Distinguished Conduct Medal, second only to the Victoria Cross, for his courage under fire on April 25, 1918 - the date of Forster's death.

Nine decades later, Nick Lynch wants to find the families of both brave soldiers.He hopes to return the original letter to Forster's descendants and provide a copy to the relatives of Sgt Parr. In the meantime, two of his four children, Eve, 13, and Seamus, 11, have carved a tribute to honour Forster's memory. They made redgum crosses to be placed on his grave in France. The crafted crucifixes are already on their way to Europe, carried by Mr Lynch's brother, Mark. Mark Lynch is joining Melbourne firefighters running a 4400km relay through Europe's battlefields from Gallipoli to London.

Despite his best efforts to date, Mr Lynch has been unable to trace relatives of either man. Forster, a dental technician, came from Maffra, but his parents, Alfred John and Mary Jane Forster, were last traced to Melbourne. They suffered another blow after Charlie's death. Not even their request for his meagre belongings could be fulfilled when the ship on which they being sent home was sunk.

Sgt Parr was born in Beeston, Nottingham, England. He came to Victoria, worked as a farmer, and signed up in Hamilton in February, 1915. The search for his family has been complicated by the different surname of his mother, Elizabeth Newbon. "Experienced people in the Maffra Historical Society have been unable to find the Forsters and my attempts to contact Parrs and Newbons in the UK have also failed to turn up anything," Nick Lynch said.

He said he was emotional when he found the letter, dated May 1, 1918, and hidden for decades in the old frame. "Charlie was a friend of a distant relative, and he had sent her both the photograph of himself and a postcard, which was also in the frame. You can see on the letter from his sergeant that someone has written in the bottom corner of it 'A very nice letter, isn't it', which may have been Charlie's mother."

Mr Lynch said the extraordinary timing of the discovery of the precious parchment highlighted the importance of Anzac Day. "Lest We Forget is what this is all about and I am determined to ensure that Charlie's and Sgt Parr's families know that we haven't forgotten them," he said. "That's why I'll move heaven and earth to track them down."

If neither family can be traced, Mr Lynch will donate the letter to the Australian War Memorial in Canberra. "This is a letter from the grave," he said. "It takes you straight to the trenches of World War I, and is a precious piece of military history. "The worst-case scenario is that if the men's family lines do not continue, we must make an effort to remember them."