In Australia and much of the world, 11 November, Remembrance Day, is a day to think of those who have fallen in war – and not only the First World War, which ended in an armistice on this date.

For me, there's a complicated additional resonance or two. Like many Australians, my family tree includes soldiers who fought for this country in the First World War. What's different about mine is that one of them was German.

Karl Wilhelm Albert Wengatz was born in the Pomeranian town of Pasewalk in 1882 and settled in Australia around 1906. Some time later he changed his name to a more Anglicised (if repetitive) Charles William Albert Williams (pictured), joined the Royal Australian Artillery and was promoted to sergeant in charge of a machine-gun section on Thursday Island in Torres Strait.

Who knows what conflicted thoughts went through his mind when Australia joined Britain in declaring war on his former homeland in 1914. What is known is that he fought against his former countrymen with the Australian 1st Siege Artillery Brigade on the Western Front from 1915 until 1918, when he was wounded in a mustard gas barrage. Family lore holds that it was friendly fire – a New Zealand bombardment that fell short. Whatever the cause, Lt Williams returned to Australia with stricken health, developed tuberculosis and died in 1929, not much older than I am now.

It gets stranger. Karl's brother – my great-grandfather, Erich Wengatz – followed him to Australia, and in 1910 married an Anglo-Australian and settled in the Hunter Valley farming district of New South Wales. It was there, a hundred years ago precisely to this day, that he was killed with a single bullet to the head. A coronial inquiry concluded it was an accident while on a kangaroo hunt. Other than my instinct for a good story, I have no strong reason to believe otherwise.

Whatever the case, Erich did not live to experience the internment and harassment of Australia's 100,000-strong German community — suddenly transformed from pillars of society to the enemy within — that intensified as the war dragged on.

Why recall their stories now?  One reason is because the centenary of a world war is absolutely the right time to draw meaning and lessons from diplomatic failure and catastrophe, especially when the international system is struggling with dangerous new currents of disorder. 

But in Australia, there's special relevance to the realisation that the celebrated ANZACs were a diverse lot – as stories such as this one also remind us. As my colleague James Brown has so eloquently noted in this book, the so-called centenary of ANZAC will soon move into full swing. It's important that these commemorations are inclusive of the wider Australian community and its modern, multicultural texture. The message should be about citizenship, duty, and the national interest, qualities that stand quite apart from heritage.

As Australian forces engage again in military operations in the Middle East, as risks accumulate in our region of Indo-Pacific Asia, and as migration from both these regions adds new political complexity to the character of Australian society, the need to build an inclusive vision of this country's approach to security and defence is more important than ever.