Codeko

<p>With this plugin you can set any post type (or posts types) as parent of any post type.</p>
<p>Urls will be wellformed, redirects will work, breadcrumbs will work fine.</p>
<p>This plugin is recomended when you need a url structure with a mix of post types. Any url structure you can imagine could be done.</p>
<p><strong>Post types rewrite slugs will be ignored</strong></p>


Custom Posts Parents

Set any post type (or types) as parent of any post type. Any post structure can be created with this plugin.

ttodua

Puvox Software

<p>[PLUGIN IS DISCONTINUED! we do not have any recommendations for alternative plugins]</p>
<h4>Plugin Description</h4>
<p>Plugin adds “parent & hierarchy” functionality to posts (If you have problems, deactivate plugin and in “SETTINGS>PERMALINKS”, do “SAVE PERALINKS” 2 times).</p>
<h4>Available Options</h4>
<p>See all available options and their description on plugin’s settings page.</p>


Custom Posts Parents vs Add Hierarchy (parent) to post