Code to add template to page

locate_template function searches your current theme’s folder for template name(s). If your templates are in a root folder of your theme, use:

$template = locate_template( 'member-content-template.php' );

otherwise, precede the name of a template with subfolder’s name ( no slash in front ):

$template = locate_template( 'templates/member-content-template.php' );

To load a template ( if found ) add true as a second parameter of locate_template function:

$template = locate_template( 'member-content-template.php', true );

Update: To load a tempate in your plugin, use filter ‘template_include’:

function my_template_loader_filter() {
    function my_template_loader( $template ) {
        $my_template = locate_template( 'member-content-template.php.php' );
        if ( ( '' != $my_template ) && is_page( 'member-register' ) )
            return $my_template ;
        }
        return $template;
    }
    add_filter( 'template_include', 'my_template_loader' );
}
add_action( 'after_setup_theme', 'my_template_loader_filter' );