Heinrich Sielwerst, a hatmaker (Hutmacher), and his wife Margaretha Wenlid settled in the Volga German colony of Katharinenstadt on 27 August 1766. They are recorded there on the 1767 census in Household No. 61.
The 1767 census records that Heinrich Sielwerst came from the Dutch town of Amsterdam in Holland.
There are no known surviving male lines of this family among the Volga German colonies.
- Pleve, Igor. Einwanderung in das Wolgagebiet, 1764-1767 Band 2 (Göttingen: Göttinger Arbeitskreis, 2001): 289.