[TYPO3] want not in menu page show up in URL

[Bing Du]

Hi,

Typo3 3.8.1
realurl 1.0.0

Here is the page tree.

mainsite
   Home
   People
   subsite
     page1
     page2

The 'subsite' has its own extension template with the 'mailsite' 
template included in the 'include basis template' box.  'subsite' is 
hidden in menu.  http://www.mainsite.edu/subsite works fine.  We want 
http://www.mainsite.edu/subsite/page1 and 
http://www.mainsite.edu/subsite/page2 to work too.  But when you click 
page1 or page2, the URL is http://www.mainsite.edu/page1.html or 
http://www.mainsite.edu/page2.html respectively.  Anyway to make 
'subsite' (even if it's hidden in menu) show up in the URL?

Thanks in advance,

Bing