Hi Phillipp,
Have you tried
Ferma? I have not, but based on its similarity to TinkerPop2's Frames, and good documentation, I think it might fit your needs. It does provide inheritance, via Java class extension, for vertex types (frames), and as far as I can tell, edge frames as well. Note also
Totorom, though the latter has not been maintained in some time.
I am not aware of any mainstream property graph schema *language* which supports inheritance. A language I wrote for company use did support vertex type inheritance for a time, but this was driven by my bias as the designer rather than a business need. These days, I prefer algebraic schemas, and composition over inheritance for most things. However, an ORM framework in Java, with OO-style inheritance, might be just what you need.
Josh