About Gylstorff genus.
North of the River Elbe, near Lübeck, one having a small village called Gylstorff, this is my theory of the family come from there, it makes no sense that it should come from Luxemborg.
Look into my hand on the family at:
http://familytreemaker.genealogy.com/users/l/a/r/Molly-Larse... for more information on the family, something you just have to remember is that there are some who took the name Gylstorff without being "born" with the name, a part of this family settled in the U.S. A.
Sincerely,
Molly Larsen