Tracey and Dern discuss Catharina's family on page 219 of Pioneeers of Old Monocacy.
According to her burial record, Catharina and Robert had 5 sons and 7 daughters, of whom 2 sons and 6 daughters were living at his wife's death in 1776; they also had 20 grandchildren.
Grace L. Tracey and John P. Dern. Pioneers of Old Monocacy: the Early Settlement of Frederick County, MD, 1721-1743. Genealogical Publishing Co., Baltimore, 1987
Frederick Sheely Weiser, ed. Record of Marriages and Burials in the Monocacy Church in Frederick County, MD, and in the Evangelical Lutheran Congregation in the City of Frederick, MD, 1743-1811. National Genealogical Society, 1982. Catharina's burial record transcribed on page 91.