to make long story short:
i have a object parented to a bone
but if i try to access that bone with "object.getParent()"
i just get a reference to the armature wich contains the bone.

So i really need to know where the information about parentbones are store in the object data!

If there is no way
then i have to rewrite parts of my vrml Armature exporter

I guess thats for Object.getParentBoneName() method exists.