The following logic works fine on the parent and children pages where a widget is supposed to appear:
global $post; return (is_page(555) || ($post->post_parent=="555"));
But I also want other widgets to not appear on these same pages. I tried the following but it blocks the widgets from appearing on all pages which is not OK while allowing it on the home (blog) page and single (post) pages which is OK.
global $post; return (!is_page(555) && (!$post->post_parent=="555"));
What am I doing wrong?