Those people listed as children here and therefore brother and sister is an assumption based on them all being a similar age and living in Colonie Brinsk. This is very likly but it is an assumption and not proven genealogical fact.
Death record Kinder listed as Gottlieb, Ludwig, Johann, Martin, and Wilhelmine
As per research by Imgard Hensel from Lutheran records for Lautenburg.
17. Christoph Koberstein and Maria Ikert had only two of their children listed in the Lautenburg records. They are:
1. Wilhelmine Koberstein was born 6 June 1834 in Colony Brinske. Witness was Colonist Engel and Elise Liske.
2. Anna Justine Koberstein was born on the 14 Dec 1837 in Colony Brinsk and christened on 24 Dec 1837 in Lautenburg. Witnesses are Wilhelm Engel and Rosine Ritter.