Post and Page under the same parent

Hi Guys, please help me to achieve the following

http://www.site.com/parentA/page1_A/
http://www.site.com/parentA/page2_A/
http://www.site.com/parentA/post1_A/
http://www.site.com/parentA/post2_A/

http://www.site.com/parentB/page1_B/
http://www.site.com/parentB/page2_B/
http://www.site.com/parentB/post1_B/
http://www.site.com/parentB/post2_B/

instead of

http://www.site.com/parentA/page1_A/
http://www.site.com/parentA/page2_A/
http://www.site.com/post1_A/
http://www.site.com/post2_A/

http://www.site.com/parentB/page1_B/
http://www.site.com/parentB/page2_B/
http://www.site.com/post1_B/
http://www.site.com/post2_B/

basically i want to collect all relevant pages and posts under the same parent, how to get pages under parent i know , but how to assign post to the same parent ?