His grave is near the top of a short hill in Hong Kong’s Stanley Military Cemetery, and each time I make the climb, as I have done many times over the decades, my breathing is a little heavier. The inscription on the tiny tombstone is simple: “Brian Gill 31 July 1940 – 9 May 1944 R.I.P.”

It gives no hint of the shock that his untimely death caused in a Japanese civilian prison camp on a summer’s day 15 months before the end of the second world war in Asia.

Brian was my older half-brother. On occasions such as Remembrance Day, I acknowledge my great debt to him. Our story is a poignant echo of the tribute we often pay to the war dead: “They died that we might live.”

Brian Patrick Hirst Gill was 16 months old when the Japanese attacked Hong Kong, on December 8, 1941. His mother, Louise Mary “Billie” Gill, a petite woman with abundant energy, was then working with the Chinese Government Information Office on Hong Kong Island.

Her husband, Arthur Robert Hirst “Paddy” Gill, an Irish warrant officer with the British army, had been transferred with his regiment to England between March and April 1940. Their brief marriage had not gone well and, as he left, Paddy had told Billie not to follow him.

Billie was ethnically Chinese but British by education and nationality. After the British surrender on Christmas Day, 1941, she joined some 2,800 civilians – mainly British, American and Dutch – in the Stanley internment camp.

Brian was a full-time responsibility but he provided Billie with the emotional and mental focus needed to endure a lengthy captivity. In Stanley, men had difficulty adjusting because they were stripped of purpose, but women fared better, continuing in their roles as family caregivers. Children adapted more easily, many leading carefree, even wild existences roaming the camp’s many green spaces on the windswept Stanley peninsula.

Brian, whose features echoed those of his father, was a calm child and not difficult to look after. Only once did he cause Billie alarm, screaming inconsolably for no discernible reason. Finally, he was laid on his back and it was noticed the soles of his feet were unusually red. He had scalded himself standing on a hot metal cover.

On May 9, 1944, friends from a Catholic women’s group offered to give Billie a break and took Brian to Tweed Bay beach, which the Japanese had opened to the internees.

Although Billie had an excellent memory, her later recollec­tion of that day was hazy. She told me she might have been on cleaning duty at Bungalow B, a former teacher’s home she shared with dozens of others. One friend recalled she was playing bridge, a distinct possibility – she had learned the game in camp and had quickly become adept; being used to 136 mahjong tiles she found it relatively easy to memorise 52 cards.

Looking up, she saw Stephen Balfour, a tall young Englishman, coming through the door, pale and breathing hard. He approached her saying, “Billie, please come with me.”

Billie froze, beset by foreboding. “What is it, Stephen? Is it Brian?” But Balfour would only repeat, “Please come with me.”

It was a few hundred yards to Tweed Bay, with a long flight of steps down to the beach, and Billie struggled to keep up with Balfour’s strides. She gasped for breath and she prayed as she had never prayed before.

On the beach, a crowd had assembled and it parted to make way as Billie approached. Brian was cradled in a woman’s arms and, for a moment, Billie hoped that he might be only sleeping. But it was not so. He had been found lying face down in a shallow freshwater pool and had not regained consciousness despite frantic efforts to revive him. The circumstances that led an active child of three years and nine months to drown – whether he had fallen and struck his head, or had been pushed – have forever remained a mystery.

The tragedy shook the camp, for very few children died in Stanley. Apart from Brian, only four of its 300-odd youngsters perished, mainly from complications during or following childbirth.

The funeral was marked by a procession of children dressed as angels, their white robes made from bed sheets. They held candles and sang “Heaven is the Prize.” The Japanese, who were fond of children, provided a tiny coffin.

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For Billie, the devastating loss was magnified by her imprisonment and lack of privacy in a place where the main activities were queuing for rations and the toilet. Brian had been her lifeline, shaping her daily routine and providing hope for the future. In the aftermath, friends said, Billie was prone to fainting spells and crying out her child’s name.

At this time, one man emerged as a pillar of support. George Giffen was an English journalist who had been a reporter and editor with the South China Morning Post and Telegraph newspapers since 1933.

He had met Billie on one occasion before the war and, in camp, had been a regular visitor to her and her friends in Bungalow B, no doubt seeking a break from the male colleagues he shared quarters with at St Stephen’s College, a short walk away. With his droll humour, George was always welcome and, as a worker in one of the gardens, he on occasion brought twigs to fuel the chatty or scraps of food. In his early 30s, he bore a striking resemblance to the American film star Tyrone Power.

There is no doubt that Brian’s death transformed their relationship. Billie, who was 25 when she entered Stanley, had learned independence the hard way but remained naive in many respects. Adopted as a baby by an English postal commissioner and his Chinese wife, she had had a privileged education at Shanghai Public School, where she excelled. At the age of 16, however, she dropped out, to help support her mother after her father left the family. In an environment in which Against Eurasians were looked down upon by both Europeans and Chinese, Billie had worked as a teletypist at the Reuters news agency and later as office manager for a literary maga­zine written by Chinese and Western intellectuals.

A good and conscientious worker, she had been seconded to the mayor of Shanghai after the Japanese attacked the city in 1937 and became a government radio broadcaster, her posh English accent and Chinese name – thinking fast, the mayor dubbed her Billie Lee – attracting a following of intrigued listeners. After Shanghai fell, she had fled with colleagues to Hong Kong, where they regrouped to establish an information agency for the Chinese government. But even with the traumas she had experienced, nothing could have prepared her for the loss of Brian.

George, knowing that his friend was close to a break­down, began to visit her more often. He was there to catch her when she fell. Often preferring to express himself in writing, not long after Brian’s death he composed a poem for Billie:

My dear, no human heart can swell,
So much as mine, no tongue can tell,
The words that are themselves too weak,
To touch the chords where grief may wreak,
Her muted anguish for a loss like yours,
Such sorrow where recompense implores,
The babe that from your womb,
Has gone, too young, to mortal tomb,
Bore all the marks of happiness and joy,
The promise of a man was in that boy.”

George’s loyalty and kindness were a revelation in one who had experienced so little of either. Born in Edwardian England, George had paid a heavy price for being the son of an intelligent and hard-working woman whose misfortune it had been to consummate a relationship she had hoped would lead to marriage, and who was ruined when it did not.

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His mother, Constance, had a secure job as housekeeper with an affluent family in Sudbury, Suffolk, when, at 29, she had a relationship with a footman and became pregnant out of wedlock. She left her position and, in March 1911, gave birth to George in Dorking, south of London, away from her parents in Cambridge. Burdened by the stigma of being an unmarried mother, Constance struggled in vain to keep her child, leaving him with minders in the village while she worked long hours as a household cook. But when George developed rickets, a sign of undernourishment, she put him in the care of St Andrew’s Society for Waifs and Strays. From around four years of age he was raised in unloving foster families and homes with tough discipline.

George grew up being called bastard. One household help would hold his head in a toilet bowl as a punishment. Fortunately, he was bright and an avid reader and, after win­ning a scholarship to a grammar school, he landed a job on a newspaper. His big break came when he answered an advert for a reporter in Hong Kong and, soon after, he sailed east to a new life.

George embraced the mores of Hong Kong and he played as hard as he worked, enjoying its fleshpots and the company of hard-drinking Australian colleagues. In 1938, perhaps as much in a bid to settle down as for love, he married Erma, a pretty Canadian girl from the harbourmaster’s office. In 1939, against the backdrop of the threat of war, she was evacuated to Canada.

Billie came to know the sensitivity behind George’s bon­homie and his cynical attitude towards officialdom and they became close companions and, eventually, lovers. Stanley, though, with its shared living quarters, posed formidable barriers to intimacy. One rendezvous favoured by couples was the cemetery, while others retreated to the dark rooftops of its buildings. The Japanese, on becoming aware of amorous liaisons, issued a diktat against “immorality”. The main constraint, however, was the fall-off in sexual desire that accompanied a starvation diet. Men would complain among themselves that they were not up to it while for women there was a more fundamental issue – poor nutrition meant many of fertile age stopped menstruating, and Billie was no exception. Stanley inmates even coined a term for the condition: “malnutrited”.

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Then, in September 1944, after years of withholding Red Cross parcels, the Japanese had a change of heart and each internee received three Canadian Red Cross packages containing such treats as corned beef, sardines and meatloaf. Evidently, as a result, Billie’s monthly cycles resumed and sometime around February 1945, she and George found a place for themselves off the quiet path, surrounded by shrubbery on both sides, between St Stephen’s and the cemetery. In an “arbor”, as she described it to me, I was possibly the last baby to be conceived in the Stanley camp.

With the discovery of her pregnancy, Billie was over­joyed. Amid the dehumanising conditions of Stanley, she felt re­affirmed both as a woman and a mother. The first time we visited Brian’s grave together, in 1975, she told me, “You were two sons rolled into one.”

I know George’s reaction to the news because Mum kept his letters from camp. His response was more measured. To mark Billie’s 29th birthday, on June 14, 1945, he wrote a poem to the “unborn baby of my unwed wife”. He said he looked forward to the baby’s arrival “with an equanimity only disturbed by the lack of suitable food for you, the diffi­culty a birth may be to you and the bearing the forcible liberation may have on your state of mind and physical condition”. Then he added: “There is so much to be said about love. We have had a great deal of each other and have meant a great deal to each other and we have consummated a union that was greater than friendship, if a little below the greatest passion, in a way that is not given to all, be they blessed by church or not.”

A few weeks later came the dropping of atomic bombs over Japan and the subsequent liberation of Hong Kong and Asia. As one of the journalists who was still in reason­able shape, George went to town with colleagues to wrest control of the South China Morning Post back from the Japanese. Over the weeks that followed, under the title of publisher, he was heavily involved in production as well as reporting and editing during the confused, chaotic period before the British navy arrived to formally assume power. He was also thinking of his wife in Canada, who had borne him a daughter he had never seen.

The days after the Pacific war ended: unsettling times in Hong Kong

He fretted over Billie, fearful she might have an emotional relapse, and wrote to her several times. I do not have her letters but George’s replies suggest she was increasingly anxious to see him. On September 7, he wrote, “I got your last chits when I returned to the hotel at 8.30 a.m. I can under­stand how upsetting all the changes must be to you.” He was also referring to the uncertainty surrounding repatriation arrangements for internees.

That same night, a Friday, believing her ship would not depart until the following Tuesday, he wrote that he intended to borrow a car to visit her early that Sunday morning. For whatever reason, he did not make the trip. On September 10, he wrote: “A hurried note to say farewell. Goodbye, my dear, for now. Don’t regret Stanley and think not too harshly of me who have [sic] done you so much harm and brought so little happiness to you.”

Billie was dejected as she boarded the Empress of Australia. The war had ended in victory, but it did not feel that way. She had begun the conflict caring alone for an infant and now she was embarking on another uncertain journey with new life inside her and alone once more.

Soon after the ship departed Hong Kong on September 12, another crisis loomed. A doctor told Billie she would need a caesarean delivery – and that the troopship was not equip­ped for the procedure. In Manila, hope beckoned with the arrival of a converted New Zealand hospital ship, the Mount Maunganui. Manila was in postwar mayhem at the time, its harbour strewn with wreckage, and few vessels were allowed to dock. After a frantic exchange of signals, there was the hullabaloo of transfer. Billie was lowered by hoist onto a small craft and taken across the water, where she was lifted aboard the hospital ship. It was an unnerving experience, being dangled in a swaying hoist supported by ropes and a pulley high above the sea, the spectacle wit­nessed by hundreds of cheering onlookers leaning overboard.

A few weeks later, on October 25, I was born in Lower Hutt Hospital, Wellington, New Zealand. Considering my adventures up until then, it was a minor sensation that I emerged at all.

Mum had many difficult years ahead of her but she told me that, in moments when she felt like giving up, she took motiva­tion to carry on from me. It was only much later that I came to understand that, but for Brian and the immense void he had left, I would likely not have been conceived at all.

Although disappointed that the love that had bloomed in captivity had not been sustained in liberation, my mother spoke only well of George, whose compassion had pulled her back from the abyss and who had given her me.

My parents did not see each other again, but she was supportive when, after a long search, I went to meet my father on a remote Canadian island in 1985. He was most welcoming and I was delighted to find the other half of my genetic puzzle. Naturally, I’d had problems growing up without a father, but I was grateful to be born at all.

As a footnote, my wife, Jean, gave birth to our twins, a boy and a girl, in 1999, and I named my son Brian. We took them to Geneva to meet my mother. There, at the airport, Mum looked at Brian and said that he reminded her of her firstborn son, and she wept. This time, her tears were more of joy than sorrow.