pantsonhead

Currently WordPress does not provide the ability to change the post that an item in the Media Library is attached to after it has been set. This plugin allows editors to change the parent post to another post.

Change Media Parent

Allows editors to change the parent post of an attachment after it has been set.

BeardedGinger

Designed to display the Parent, Child, and Grandchild hierarchy in the most straightforward way out of the box.
This plugin will provide a widget that locks the Parent page as the widget title.
If this is a child of the top parent, the widget will display the Parent as the title of the widget and a ul of links for all siblings of the current page.
If this is a grandchild of the top parent, the Widget will display the same as the scenario above with the addition of a sub ul of all siblings of this grandchild.
Test it out, if it doesn’t work like you want out of the box, this plugin isn’t for you.

Simple Page Hierarchy Widget

Displays the most logical arrangement of Parent, Child, & Grandchild pages.

Change Media Parent vs Simple Page Hierarchy Widget