将所有子页面重定向到父主页

I have website like www.example.com and this page already redirected to www.newdomain.com, The rediction rule written in somewhere. not in the root directory.

When I enter www.example.com/about-us its redirected to www.newdomain.com/about-us and says 404 page not found. I want to redirect all subpages from example.com to example.com home page.

I used following code but its not working.

RewriteEngine On
RewriteRule ^parent/(?!index\.php).+)$ /parent/index.php [L,NC]