How can I list the current pages siblings and any ancestor page siblings?

You can get top levels page id with following function

function find_top_level_id( $post_id ) {
   $ancestors = get_post_ancestors( $post_id );

    if ( $ancestors ) {
        return end( $ancestors );
    } else {
        return $post_id;
    }
}

You can use the returned value with wp_list_pages()