The First Ancestor of Arntz
The (re)search is still going on, but Steven Arntz currently seems to be the oldest known ancestor of the Arntz family that is also still present in Belgium and the Netherlands.
Steven Arntz is mentioned as tenant (“pachter” in Dutch) of a Mr. van Bronkhorst during the years 1577-1580. Definitely in Duffelt, but not (yet) with an exact location.
The name of Steven Arntz his wife is yet unknown, but his son was named Peter Aerntsen (also mentioned as Arenssenn, Arndtzenn and Arntz). In 1625 Peter was a churchwarden (“kerkmeester” in Dutch) in Mehr (Germany) and he deceased after 1661.
All this informatian is based on the great research by Guido van Benthem and Arie Leeuwrik, as mentioned on http://www.arieleeuwrik.nl.