Maven Site - Multi Module Project - Grouping of Submodules

Question

I am generating a site using the maven site plugin (version 3.4). My project(-pom) structure is as follows:

Root
  +--Sub1
  +--Sub2
  +--Sub3
       +--SubSub1
       +--SubSub2

Unfortunately in the "Root" about site, where the modules are listed, also the SubSub modules are listed, whereas the folder structure in the staging directory correctly represents the project structure.

Is there a solution for this? Basically I do not want to show the SubSub modules in the root site about page.

Thank you in advance!