The Geneva Refugee Convention passport (also called “blue passport” or Geneva Passport) is only recognized as a travel document by the 145 countries worldwide that have joined the Geneva Refugee Convention (GRC). Unfortunately, the United Arab Emirates (which includes Dubai) have not joined. Most of the arab countries have not signed this convention.
In Germany, a German passport renewal or a new application can only be done by the German person himself. This requires an appearance in person. I can imagine that this is also the case in Syria. The father-in-law could then not apply for a Syrian passport for your friend in Syria.
However, I would advise against it, even if it is possible, because your friend has a GRC passport and fled Syria. If he applies for a new Syrian passport in Syria or the Syrian embassy in Berlin, he could risk losing his recognized refugee status in Germany. Can he meet his family in another country? In Egypt, Ethiopia, for example? A list of countries that have joined the GRC (i.e. that recognize the GRC passport) can be found by your friend at.
This article was first published in German,