Rosina Mertz is on find-a-grave, buried in Alsace Manor. I don’t know who else it could be other than this Rosina.

The records of Moselem Church note the 1756 marriage of Johannes Mertz and Rosina Haffa and say that Johannes, a wheelwright, was the son of Johannes “aus dem Wurtenburgishem Stochenhausen” (from Stockhausen in Wurttemberg, Germany). That record was written by the minister who married this couple and I have seen other similar citations for immigrants which named the father back in Germany and I have no reason to think it wrong.

Now there are some people who state in their family trees that John Henry Mertz, founder of Mertz Church, was from Stockhausen. For example, my father’s cousin who did his genealogy in about 1970 told me, mistakenly, that I was descended from John Henry and he also told me, mistakenly, that John Henry came from Stockhausen. (When I later went to Germany and asked German friends where Stockhausen was, they said it just means “a village” as opposed the name of a particular village.)

But the truth is the record says that about Johannes and only Johannes. So either people totally misunderstood that fact or they assumed that John Henry was a brother to Johannes. But that can be ruled out since we now know the name of John Henry’s father (it was not Johannes) and the names of his brothers (there was no Johannes) and where John Henry was from (it was not Stockhausen).

It is a fact that Johannes, John Henry and Jost all worshipped at Mertz Church at some time and that seems to be where they all started out in the new world. Later, they and some of their descendants migrated from there. So, they may have been related, for example cousins of some sort. If we could ever find a known descendant of Johannes, then his DNA could prove whether or not John Henry and Johannes were related or not. Until then, I just don’t know.

Johannes gets the single letter designation J. He is one of the five Mertz “original American ancestors” who settled in Berks County. The other three “original American ancestors” settled elsewhere.

Johannes and Rosina were named twice in the records of Oley Reformed too, as sponsors, in one case for a son of Christoph Gerhard in 1764 and the other for the son of Johannes Friederich and wife Eva in 1766. It is curious their associations at times with Mertz Church, at times Moselem and at other times with Oley and also interesting that their marriage was recorded at both Moselem and Mertz Church.

Johannes and his male descendants to 1850 are covered in the Mærtz Hierarchical Project:
https://www.mertzgenealogy.com/names/johannes_mertz_family_j.pdf

The thing I don’t know for certain is whether Johannes was the immigrant of that name who came in 1749 or was instead the immigrant listed as Hans Martz who came in 1751. I had always thought Johannes was the 1749 immigrant as that is what Morton Montgomery said but then I read a published family history that mentioned Johannes (the one associated with Mertz Church) as the other guy -- Hans in 1751. I consider neither source authoritative and will simply say I don’t know which was Johannes (though I still lean to the 1749 guy) but it really doesn’t matter. We’re discussing here the Johannes associated with Mertz Church. I think he arrived 28 Sep 1749 on the ship Ann.

In the Annals of Berks County, Montgomery tells the story of Johannes Mertz. He was the son of Johannes of Stockhausen, Wurttemberg. He emigrated in 1749 and married Rosina Hase daughter of Melchior in 1756. Their children were Johannes 1757, Anna Maria 1760, Maria Salome 1763, Melchior 1765 and Peter 1769.

The estate of John Mertz, wheelwright of Maxatawny, entered administration 13 May 1773 with Rosina the widow as administrator. (Her sureties were from Maxatawny Township, Oley Township and Reading). I have examined his estate file, unfortunately there are no clues as to the names of his children.