I am researching the same line. I have Charles (Feuerstein) Firestine b. 1813 who married Margaret from Ireland (or Germany) depending on the documentation, and had his first son named Joseph Firestine.Other children were Charles, Mary A., Catharine, Conrad, and George according to the 1851 Canadian Census.
Joseph married Elizabeth Weber of Ontario.I cannot quite make the connections yet but this linage ties into the Eby Shantz lines.
They had a son named George Henry Firestine b. 17 Nov 1877.He married Ella Catherine Bolduc (b. 05 Feb 1877) on April 24, 1901 in Waterloo, Ontario, Canada.
Clearly as the Mennonite history discusses, this family seemed to have migrated from Germany or Alsace France to Franklin County (and later Beaver and Cumberland counties) Pennsylvania very early (1686)and then migrated to Berlin, Ontario, Canada with the famous Eby family around 1815.
I am researching this line with great effort.Any information you have to share or correct is much appreciated. I am happy to share what I have so far.The historical documentation up to Charles Firestine is superb.