jeff.cave

This plugin provides a “Sub Page” widget. It lists all of the pages which are children of the current page. If there are no children, it will not display.
Options include:
<ul>
<li>title (obviously)</li>
<li>“No Sub-pages” text instead of blank (configurable)</li>
<li>hide widget when no sub-pages</li>
<li>show siblings when no sub-pages</li>
</ul>
While this is a small widget, I have attempted to make this as configurable as possible, with clean and efficient code (this is a small widget, and shouldn’t slow your site down).

PS Sub-pages

Shows the child pages of the current page. Configurable title, show siblings (or not), and "no child" text

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.

PS Sub-pages vs Simple Page Hierarchy Widget