Wordpress custom post type: parent child relationship

[admin]

How can I maintain parent child relationship in custom post type without using any plugins in wordpress ?

For eg:
when you visit this site

<blockquote>
<a href="http://www.volunteeringnepal.com/" rel="nofollow">http://www.volunteeringnepal.com/</a>
</blockquote>

you can find volunteer impact menu. Under this menu I've made

volunteers_impact

taxonomy to categorized the volunteer impact by using Plugins called gdcpt custom post type. But I want to do this without using any plugins, and most important thing is that I want to maintain parent child relationship.

In this site, when you click

<blockquote>
www.volunteeringnepal.com/volunteers_impact/volunteering-impact-2013
</blockquote>

you will find volunteer impact of 2013 only. The taxonomy name is

voluteers_impact

, but I want to keep taxonomy name

volunteer-impact

which is good for SEO purposes.

While giving custom post type and taxonomy name, this plugins suggest to use only underscore to join two words.

When you click single page suppose

<blockquote>
<a href="http://www.volunteeringnepal.com/volunteer-impact/women-empowerment-2013/" rel="nofollow">http://www.volunteeringnepal.com/volunteer-impact/women-empowerment-2013/</a>
</blockquote>

you will see the difference of post name (volunteer-impact) and taxonomy name (volunteers_impact). How can I categorized it so that url structure would be same. For eg:

<blockquote>
volunteeringnepal.com/volunteer-impact/volunteering-impact-2013
</blockquote>

for taxonomy and

volunteeringnepal.com/volunteer-impact/women-empowerment-2013