You can always make use of the page_template
filter to tell WordPress to use a specific page template for all child pages of a certain parent. It is as easy as creating a special page template, lets call it page-wpse-person.php
.
Now it is as easy as including that template whenever a child page of people
is being viewed. For the sake of example, lets say the page ID of people
is 10
add_filter( 'page_template', function ( $template ) use ( &$post )
{
// Check if we have page which is a child of people, ID 10
if ( 10 !== $post->post_parent )
return $template;
// This is a person page, child of people, try to locate our custom page
$locate_template = locate_template( 'page-wpse-person.php' );
// Check if our template was found, if not, bail
if ( !$locate_template )
return $template;
return $locate_template;
});