parent and child page woes

I have been trying to figure a solution for quite sometime without having to make more template pages regarding displaying sub pages when you are within a parent section. I also would like those children to stay up if you are viewing one of its siblings. I’ve tried a few things I found in the forums but have not had any luck, does anyone have any examples?

you can see what i am trying to attempt here.
DDp

here is the code i am working with. i have tried to exclude the parents for the other pages but it doesn’t seem to work…I’m missing something.

<div id="mainNav">

				<div id="demo"><a href="/demo-reel/"><span>DEMO REEL</span></a></div>
				<div id="commercial"><a href="/commercial/"><span>COMMERCIAL</span></a></div>
          		 <ul><?php
					if (is_page( )) {

  					$page = $post->ID;

  					if ($post->post_parent) {
    					$page = $post->post_parent;
  					}

  					$children=wp_list_pages( 'echo=0&depth=&child_of=' . $page . '&title_li=' );

  					if ($children) {
    					$output = wp_list_pages ('echo=0&depth=&child_of=' . $page . '&title_li=');
  					}

					}

					echo $output; ?>
                   </ul>
				<div id="docubites"><a href="/docubites/"><span>DOCUBITES</span></a></div>
          		 <ul><?php
					if (is_page( )) {

  					$page = $post->ID;

  					if ($post->post_parent) {
    					$page = $post->post_parent;
  					}

  					$children=wp_list_pages( 'echo=0&depth=&child_of=' . $page . '&title_li=' );

  					if ($children) {
    					$output = wp_list_pages ('echo=0&depth=&child_of=' . $page . '&title_li=');
  					}

					}

					echo $output; ?>
                   </ul>
				<div id="candy"><a href="/candy/"><span>CANDY</span></a></div>
          		 <ul><?php
					if (is_page( )) {

  					$page = $post->ID;

  					if ($post->post_parent) {
    					$page = $post->post_parent;
  					}

  					$children=wp_list_pages( 'echo=0&depth=&child_of=' . $page . '&title_li=' );

  					if ($children) {
    					$output = wp_list_pages ('echo=0&depth=&child_of=' . $page . '&title_li=');
  					}

					}

					echo $output; ?>
                   </ul>
				<div id="about"><a href="/about-us/"><span>ABOUT US</span></a></div>
				<div id="contact"><a href="/contact/"><span>CONTACT</span></a></div>

			</div>

Thanks for any guidance.

kmaier