Express posts provides a widget to display either a subset of posts, the children of a page or its siblings.

Create visual hierarchies of site pages. Options to list all pages, subpages, current page siblings. Also able to show page featured image and custom excerpts.

The total in-page navigation solution for Wordpress. Using the shortcodes and widgets provided you can display navigation between your parent, child and sibling items in any format you can think of. Additionally by way of shortcode allows category post functionality.

Nothing really too complicated here, just a way to list the all sub pages (and siblings) of the page you're currently viewing.