I guess if you are really
trying to relate the 2 mechanically, then I'm sure you can find enough similiarities to call the "cousins". But, by that same logic, the SKS is included in books geared towards the AK-47. Also the VZ58 is very
similar to the AK in useage.
I guess I kinda look at these weapons as ALL being part of the same classification, with some differences and similarities. The Israeli Galil is along those lines as well.
All great, in their own way.