William Sierks was a brother of Hans Sierks. Both William and Hans were residents of Ida County; William lived there for several years around 1900 and Hans lived there even longer around 1900 until after 1910.

William eventually was murdered in Sioux City, Iowa in 1910, following a quarrel with another man over a horse. William was married to Clara Hochstrasser who had lived in Ida County for many years.