Hi, my mother's birthname is Theis and our family comes from the borders to Luxembourg. Apparently I am not related to this branch of the family though.
I just wanted to say that the french name Jean does not neccessarily point to Luxembourg as origin, as the rhine-county has often been occupied by the french and in my grandparents' generation the name Jean was still very common at my place (which is not far from Cologne).
Just to make sure, that the search is not started in a too small area.
Besides: many german parishes have recently started printing "family-books", as e.g. the parish of Auw where my mother came from. They are quite informative if you once know where to search your ancestry.
so long Gerd Gallus, Grevenbroich-Gustorf, Germany