[TYPO3] Show the page title of the section home page

[rocky Ou]

Hey all,

I have a page tree look like this

/*************Page tree begin***************/
page 1 <!---Parent page title ---->
    sub-page 1  <!--Subnavigation begin--->
       sub_subpage1
       sub_subpage2
    sub-page 2
    sub-page 3  <!--subnavigation end-->
page 2
page 3
/***********Page tree end ****************/

When the visitors click on 'page 1', A section called subnavigation will 
show subnavigation page titles as the menu items and above these menu 
items the 'Parent page title' will be shown.

right now I'm using
lib.subnav=COA
lib.subnav.10=TEXT
lib.subnav.10.data=page:title

It only works when visitor click on page 1, if they click on sub-page 1 
  the above Typoscirpt will throw sub-page 1 to the screen not expected 
page 1. Is there a way which can help me fix the problem?

Thanks a lot in advance!
Rocky