Custom page template for multiple pages

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;
});