Of course I erred when I identified William B. McCaig as William B. Hepner.
As to the Rachael/Emma issue -- I just reported the facts as they are recorded. Was there a second Jacob T. Hepner who married a sister of Ellen perhaps? I don't think so. But I may be wrong. You might be surprised at how fast and loose the early German settlers were with their naming practices.
Keep in touch. Let me know what your research into the Hepner family turns up.