Getting book pages in same level like getting child pages I have a book called courses with several subpages, I want to show the list of ot other subpages when one subpage is open.

Example: 

-Courses
---Course1
---Course2
---Course3
---course4


I want to show course1, course2 &amp; course3 when course4 is open. I know to get childpages, but have no idea how to get pages in same level. I am using Drupal 7.
If book module is enabled, it also creates a block called "Book navigation". You can display the block in any of the "Region" defined in your theme (e.g. "Sidebar first" in Bartik theme), by visiting http://your-site-url/admin/structure/block.

The block will be displayed(in the selected region) whenever you open the book page. And by default it will show the the book pages at the same level(sibling) pages.