American Divorce-Children in Germany

Please don't respond within the quote block. I almost missed that you had responded to me.

When did W first move to Germany? She is a German Citizen

That doesn't answer the question, but I'll assume you're indicating she was born there and that the answer is sometime prior to the mid-80s.

Your follow up post tells me that H and W lived together as a married couple for just over 9 years.

Considering Georgia has a 6-month residency requirement, I'm highly skeptical that H was able to move there in March 2018 and have a divorce become final in December 2018.

I'm also highly skeptical about the validity of any child support order entered by the Georgia court since W and the children apparently never lived in Georgia. However, if W submitted the jurisdiction of the Georgia court for this purpose, then the order should be valid.

That being said, a German court is never going to know anything about the existing Georgia divorce decree unless W informed the court or H enters an appearance in the German proceedings and advises the German court about the Georgia decree. H will need to consult with a German attorney about this. On the other hand, if H never intends to go back to Germany, any order a German court might enter is probably a non-issue unless W seeks to enforce the German court order in the U.S., at which point H probably can object.