Page is ancestor of?

Assuming your page object is in $post (like inside a normal post loop):

<?php
if (in_array("95", $post->ancestors)) {
    echo "page id 95 is an ancestor of this page";
}
?>

I am looking to display a sub-navigation in the sidebar of all the child pages for a parent page. Is this the best way to achieve this?

Could look at some examples using wp_list_pages().

Yes, thank you. ??

Here is my end result for those that come across this thread:

// [not shown] special cases for post categories up here (using is_ancestor_of function)

// now for the pages
elseif(is_page()) {
	//get post id
	global $post;
	$page = $post->ID;

		// Some Menu for a set of pages
		if($page == "68" || $post->post_parent == "68" ) { ?>
			<h3>Some Title For this Set of Pages</h3>
			<ul>
				<?php wp_list_pages('orderby=name&child_of=68&title_li='); ?>
			</ul>
		<?php }

		// Another Menu for another set of pages
		if ($page == '751' || $post->post_parent == "751" ) { ?>
			<h3>Some Other Title For this Set of Pages</h3>
			<ul>
				<?php wp_list_pages('depth=2&child_of=751&title_li='); ?>
			</ul>
		<?php }
} else { ?>
// standard sidebar stuff for untargeted pages or posts