He was born in The Hague on July 28, 1863 and developed a lifelong interest in chess at the age of fifteen and was exposed to Christian anarchist Ferdinand Domela Nieuwenhuis during his early life. After graduating from Delft University, he moved to England in 1884 to become a teacher.

Siebenhaar sailed to Western Australia in 1891 and joined Perth High School’s staff as a teacher. In 1892, he became the unofficial Western Australian Chess Champion and took over the chess column in The Western Mail. In 1895, he joined the public service as a sub-editor of the Western Australian Yearbook and eventually rose to the positions of Government Statistician and Registrar-General.

Siebenhaar’s translation of the first edition of Ongeluckige voyagie van’t schip Batavia, titled “The Abrolhos Tragedy,” was printed in The Western Mail in 1897. This translation, a third-person transposition of Francisco Pelsaert’s original journal of the 1629 shipwreck of Batavia, generated significant interest across Australia and remains the only English translation of Ongeluckige voyagie. He was the first to generate more interest in the Batavia and its gruesome story and was thus influential on the interest in the actual wreck of the Batavia and the stories, movies, books and even an opera that have followed since.

In 1910, Siebenhaar founded the literary magazine Leeuwin, It only ran for six issues but featured four contributions by A. G. Stephens on ‘The Manly Poetry of Western Australia.’ The same year saw the publication of his Dorothea: A Lyrical Romance in Verse in London, which would later be scrutinized for sedition.

Siebenhaar married Lydia Bruce Dixon during a visit to Britain, where he may have had contact with Peter Kropotkin. He returned to Western Australia in late 1913 and became heavily involved in social movements such as women’s suffrage and the anti-conscription movement. In 1916, his participation in the latter movement led to his removal from the public service, with a press release condemning him as a “German” in league with the Industrial Workers of the World (IWW). An inquiry later exonerated him of disloyalty and reinstated his position with restitution.

Siebenhaar’s Sentinel Sonnets, co-authored with Alfred Chandler, were published in 1919 as a eulogy for anarchist Monty Miller. He also contributed to James Sykes Battye’s Western Australia: a history from its discovery to the inauguration of the Commonwealth and various newspapers and magazines, reflecting the views of the Theosophical Society, of which he was a member. Siebenhaar continued to write and critique poetry, engaging in debates with early poets such as Edwin Murphy, whose style contrasted with his own romantic approach.

Siebenhaar returned to England in 1924, residing in Findon, Sussex. In 1927, he translated Eduard Douwes Dekker’s Max Havelaar, with a preface supplied by his friend D. H. Lawrence, whose left-wing activist Willie Struthers in the novel Kangaroo was possibly based on Siebenhaar. Siebenhaar died from injuries sustained in a motor car accident on December 29, 1936, in Littlehampton, West Sussex.

The Abrolhos Tragedy – as published in the Western Mail – Christmas 1897