Nolan Altman recently posted a ViewMate page of WWI personnel register.
It seems that he's gotten a complete translation, but in the past I've
had similar pages for family members that were peppered with
abbreviations I wasn't able to find in German abbreviation webpages. If
you run into a case like that, there is a German email group called
milex.de that is devoted to WWI. They have members who know a great deal
about these abbreviations and can point you to links about information
regarding your family member's unit.
Kihei HI USA