Joseph Seiler was not an immigrant and I really don't have enough information about him to write a post. But I've found some hints and they tie in with what I've learned while researching other Harshbarger line families, so I'm willing to put these ideas (not my own) out as a hypothesis.
Joseph Jacob (or possibly Jacob Joseph) Seiler was born in 1687 in Wilstein, Germany, a small town
that currently does not seem to be on a map. His father's name was Joseph, and it's unsure which name our subject used. Typically, if his name was Joseph Jacob he would have gone by the name of Jacob and documentation seems to support this, but many online sites call him Joseph.
The interesting thing to me is that this was a Mennonite family, but we don't know how long the family had been followers of Menno Simons. For one thing, Joseph Jacob had at least six children, born in four different cities. This would not be typical of a German line, but indicates that he owned no land and that he either may have been ejected from each village, or forced to leave for economic reasons. Either scenario is typical of the Mennonites of the time, who were heavily fined and harassed by local authorities, due to pressure from above.
The other item that points to a Mennonite belief system is that Joseph had a book printed in 1571, written by Menno Simons, and Joseph had hand-written in it the names of his 7 children, where they were born, (Wilstig, Sembauch, Obermelingen, Ischbach), their birth date, and the astrological sign they were born under. Apparently at least at this time the astrological sign was an important factor in the Mennonite life.
I've seen speculation that this family may trace back to Emmental, Switzerland but no real evidence this is the case. If true, again it would tie in with what we've learned of the Swiss Mennonites who were forced out of Switzerland and into a life of poverty in Germany. It makes sense.
The only other thing I can tell you about Joseph Jacob is that he died January 19,1739/40 in Milsbach, Germany. It is uncertain whether more will ever to found about this family, because the Mennonites lived mostly "under the radar", except for the tax collector. But perhaps with persistence, and cash, more could be learned and we would know whether this family also traces back to Switzerland. We do know two of his sons came to America, and that is what matters most in our family history!
The line of descent is:
Joseph Jacob Seiler-Anna
Daniel Seiler-Hanna Gerber
Catherine Sayler-Johannes Buchtel
Solomon Buchtel-Maria Margaretha Reber
Benjamin Buchtel-Barbara Burkholder
Nancy Fannie Buchtel-Adam Kemery
Della Kemery-William H. Withers
Goldie Withers-Grover Harshbarger
Cleveland Harshbarger-Mary Margaret Beeks