We'll create fresh WordPress site with wp_list_sub_pages installed. You have 20 minutes to test the plugin after that site we'll be deleted.
This WordPress plugin is oly one function. It takes exactly the same parameters as wp_list_pages, except for child_of, which is used internally.
When called on in template file, it will list :
* on the homepage of the blog, every page and subpage (default, this can be overriden by parameters)
* on every other page, only the pages with the same top-parent (parent of level 1)