Our project is growing and we now have five sets of matched people. I have named the sets: Alsace and/or Longswamp, Pomerania, Mertz Church, Rockingham and I-M223 (Theobald).  Here's what I know:

Alsace and/or Longswamp

I belong to this group. 

I have traced my ancestry, genealogically, to the David Mertz mentioned in the Project Background statement.  He came to America in 1733 from Hangviller, Alsace.   One of the people I match has also traced his ancestry to Alsace -- but not to David.  His immigrant ancestor was named Gottfried Mertz and he came from Preuschdorf, Alsace to the St. Louis area in the 1840's.  One other member lives today in Alsace (now France) and can trace his ancestry to David's brother.  I believe all other members of this group descend from David.  

Preuschdorf and Hangviller are close enough that it is not unreasonable to assume that my David was a, maybe 2nd or 3rd, cousin of an ancestor of Gottfried.

David's descendants moved by 1790 to Northumberland County, Pennsylvania.  Five brothers, grandsons of David's made that move.  For three of them, the name came to be spelled Martz for them and their descendants ever after.  And for the other two, the Mertz spelling was retained.

Pomerania

Two of our members match each other and both have (independently) traced their ancestries to a person from Stolp, Pomerania -- not the same person I might point out but obviously related somehow.

Mertz Church

Several members of this group can trace their ancestry, genealogically, directly to John Henry Mertz, founder of Mertz Church.  But several can only trace their ancestry to a person who lived by the 1800's in Western Pennsylvania in one case and Eastern Ohio in the other but in both cases their ancestry seems clearly to trace back to Berks County and in fact to Mertz Church.  They may or may not be direct descendants of John Henry Mertz.

We also have one member who traces his ancestry to Jost Mertz who we now know was a brother of John Henry.

I-M223

A very interesting and surprising group, with, currently, four members, all assigned to Haplogroup M-223.

Two of them descend directly from Theobald Martz who married and baptized children at the Evangelisch church of Klingenmuenster, Pfalz, Bavaria in the years 1743-1752 and then was next named as a baptismal sponsor in Frederick, Maryland in 1753 where he then lived until his death in 1786.  FTDNA confirms these two as cousins with a genetic distance of 3 at 37 markers.   

The other two descend from George Mertz, a 1732 immigrant to America who settled in Heidelberg Township, (then) Northampton County, PA.  George was baptized by his father Peter at the Lambshein Reformed Church and he married at the Weisenheim am Sand Reformed Church.  FTDNA confirm these two as cousins with a genetic distance of 1 at 37 markers.

From American records, there is no reason whatsoever to suspect these two immigrants were related — except perhaps for this:  George had a grandson, I believe, named Theobald and that Theobald named one of his sons Theobald — and those two are the only other persons named Theobald Mertz or Martz in all of America that I am aware of.  But in addition to their common haplogroup, what is most intriguing is that one of the descendants of George is said to be a cousin of one of the descendants of Theobald with a genetic distance of 4 at 37 markers.

Visual inspection of all four certainly makes it seem their Y-DNA is quite similar one to another, it’s just a question of genetic distance being close but not close enough that statistically FTDNA would call them cousins.  I think all four are distant cousins.

Now the place Theobald is found in Germany is about 75km from the place George is found.  George was born in 1702, Theobald, I would guess, closer to 1720.  Were they brothers?  Possibly.  Cousins?  Possibly.  We don’t yet know.  If brothers, you’d think even though Theobald came 20 years later than George, he might have sought him out.  So I sort of lean to cousins.    

Rockingham

We now have three members all of whom descend from Sebastian Martz who was the progenitor of the Rockingham, Virginia line of Martzes who spread out from there in the early-mid 1800’s.