 John Sebastian Helmcken was born in London, England, the son of ethnically-German parents Claus Helmcken and Catherine Mittler.His education was at St. George's German and English school, and after apprenticing as a druggist and physician, at Guy's Hospital.He was hired aboard the Hudson's Bay Company's "Prince Rupert" as a ship's surgeon on its 1847 voyage to York Factory, Rupert's Land.