I've been using the following menu control to show sibling pages in the side bar of my third level pages.
<% control Menu(3) %>
<li><a href="$Link" title="Go to the $Title.XML page" class="$LinkingMode<% if First %> top<% end_if %>"><span>$MenuTitle</span></a></li>
<% end_control %>
What I want to know is if there is a way to show all sibling pages in the sidebar, regardless of the level - so regardless of how deep in the site, the sibling pages will always show in the sidebar?