Robert was born in Prussia, and I'm guessing emmigrated with brothers Herman and Theodor, and a probable sister, Augusta, all of whom were also born in what became Germany. I've found nothing to suggest their parents emmigrated with them, and no indication as to who they might have been.
As far as I can determine, there are no Pabitzkys in the United States now except for descendents of our ancestor, Robert. No descendents interested in family history have been able to identify his parents yet.
Robert was married to Margaretha Dobblemann in Saint Louis, but lived and died in Illinois. He owned a sawmill, had only the one child, son William Frederich. Margaretha died when William was quite small; Robert remarried, Anna Nelson, and died a few years later without additional issue.
Most of the information I have is given on the Pabitzky family website. I'll be doing more research this summer, and hope to find additional information.