Here is the block of code I use to display the page title of the top parent menu item on a sub (or child) page of that menu item.
Copy this code:
<?php
$title = $c->getCollectionName();
$parentPageId = $c->getCollectionParentID();
if ($parentPageId > 1) {
$parentPage = Page::getById($parentPageId);
$title = $parentPage->getCollectionName();
}
?>
<h1><?php echo $title; ?></h1>
And paste it into the template where you want the parent item page title to appear.
Using this code, the page title of the top-level menu item relative to the page the viewer is on will always be displayed. For example, if this were your site map:
Home
About
History
Mission
Contact
Directions
Contact Us
Using the code above, you could display the page title About when you are on the History page or the Mission page, and the page title Contact when you are on Directions or Contact Us.