The importance of online family trees often lies in their uncertainty

In creating a digital family tree from a fragmented past, I learned that accuracy often yields to the necessity of a personal narrative
The author's family. Photograph: Emily Kasriel

Start with the person you know best: yourself. Input details: date of birth, place of birth, gender, photo. You are now presented with four options pointing horizontally and vertically, like arrows in a chess book. You can travel like a rook but with the limitations of a king. Which other moves can you make? Father, mother, child, sibling, but only one square at a time. Choose another character, and repeat.

It is hardly surprising that creating online family trees has become such a popular activity. The raising of $25m (£15m) by in its fifth round of funding reflects how this interest has dovetailed with the power unleashed by the internet: the ability to transform our ability to research, share and collaborate, liberating us from the limitations of unwieldy paper predecessors.

Family Records Centre
The Family Records Centre in London. Photograph:Martin Godwin Martin Godwin/martin godwin

My experience of putting my own family tree online has proved to be both exhilarating and frustrating. I was surprised and disappointed to find how quickly I reached the frontier of my knowledge. My father Harry and his parents fled Czechoslovakia in 1938, prescient of the impending Holocaust, which was to erase most of their family.

I dug out a fragment of paper on which, as a teenager, I had recorded the names of my grandmother's six brothers and sisters, born in the Austro-Hungarian empire in the final decade of the 19th century – only one had survived the war. I remember being aware, even then, of the fragility of my link to the past.

More than two decades later, I regret that I was not more persistent at a time when my grandparents' stories had not yet been distorted by the frequent repetition of a few highly distilled fragments: swimming across the Danube, picking wild mushrooms in the forest, skating on the lakes in the freezing cold winter. Part of my drive to capture this information is a desire to grasp it and tie it down. What I find ironic is that the virtual world can be the locus for reifying these elusive moments from my history.

In drawing up my tree, I have found that it is the connecting fibres and portraits of the uncertain or unknown that become the most compelling. In her memoir Things I've Been Silent About, Azar Nafisi writes of becoming obsessed with the photographs of her mother, whose enforced silences and constructed truths about her past exerted an almost tyrannical pressure on the author's life. Nafisi became "a memory thief", collecting photographs of her mother alongside pictures of the old Tehran in which she grew up. The author writes that the photographs, the descriptions, even the facts are insufficient. "What I am searching for is the gaps, the silences. This is how I see the past: as an excavation."

One cousin of mine has been hesitant about collaboratively publishing our family tree. For him, it felt like I was setting facts in virtual stone that may have only an ambiguous relationship to reality. Over the generations, if these online family trees last that long, details of half-remembered relatives could become established facts and become hard to dislodge from collective memories. I believe that we all need stories so we can make sense of the world. We sometimes create memories to replace absences, and these are important for the construction of our identity, even if some are not wholly accurate.

Once my tree had sprouted with the names of great aunts and distant cousins, it became a blossoming structure on which I could hang the sepia-toned images of promenades in the prewar spa towns of central Europe. Other online family sites give you the option of scanning in images and then tagging the protagonists, so these portraits appear on their profile and your tree. I am drawn to the idea of these extinct relatives being part of a 21st-century social network, even if these individuals died many decades ago.

Perhaps the desire to be rooted, to create a structure of our past to replace what is unknown, is the fate of the modern cosmopolitan. When you have grown up in a different country and culture to your parents, whose families in turn were cast far and wide by the maelstrom of the 20th century's political horrors and economic uncertainties, the goal of capturing these names, births and deaths is enticing. The reality is more elusive. I can only ever achieve a partial grasp of a truth that will never be illuminated in its entirety. But as we are all becoming more mobile, more likely to break free of our physical roots, I see such businesses' success being just a starting point for a proliferation of families using digital tools to capture our ever more disparate histories and stories.