I couldn't get the breadcrumb trails (menu) to work with my pages / stories that I structure with node relativity (a Drupal module). I don't know if I'm doing something wrong, but looking at the code, I couldn't see any support for it. So, here it is, a quick and dirty hack to add the breadcrumb trails to your node relativity structures:

--- relativity.module-2.4       2008-09-17 19:44:07.000000000 -0700
+++ relativity.module   2008-09-18 07:49:10.000000000 -0700
@@ -378,6 +378,14 @@
     '#title' => t('Global Options'),
   );
 
+  $group['global_options']['relativity_breadcrumb_trails'] = array(
+    '#type' => 'checkbox',
+    '#title' => t('Update the breadcrumb trails menu'),
+    '#return_value' => 1,
+    '#default_value' => variable_get('relativity_breadcrumb_trails', 0),
+    '#description' => t('If checked, the ancestor hiearchy of the page is used to create the breadcrumb trail menu.'),
+  );
+
   $group['global_options']['relativity_allow_types'] = array(
     '#type' => 'select',
     '#title' => t('Node types that can be involved in relationships'),
@@ -1067,13 +1075,35 @@
       break;
 
     case 'view':
-      if ($w = variable_get('relativity_'.$node->type.'_ancestor_weight', 0)) {
+      $do_breadcrumbs = variable_get('relativity_breadcrumb_trails', FALSE);
+      $ancestors_w = variable_get('relativity_'.$node->type.'_ancestor_weight', 0);
+
+      if ($do_breadcrumbs || $ancestors_w) {
         $ancestors = relativity_load_ancestors($node);
+
         if (is_array($ancestors) && count($ancestors) > 0) {
-          $node->content['relativity_ancestors'] = array(
-            '#value' => theme('relativity_show_ancestors', $node, $ancestors),
-            '#weight' => $w,
-          );
+          if ($do_breadcrumbs) {
+            $breadcrumb[] = l(t('Home'), NULL);
+            foreach($ancestors as $ancestor) {
+              if (!is_array($ancestor)) { // Only handle single ancestors here
+                if (array_key_exists("path", $ancestor)) {
+                  $breadcrumb[] = l($ancestor->title, $ancestor->path);
+                } else {
+                  $breadcrumb[] = l($ancestor->title, 'node/'. $ancestor->nid);
+                }
+              }
+            }
+            if (count($breadcrumb) > 1) {
+              drupal_set_breadcrumb($breadcrumb);
+            }
+          }
+
+          if ($ancestors_w) {
+            $node->content['relativity_ancestors'] = array(
+              '#value' => theme('relativity_show_ancestors', $node, $ancestors),
+              '#weight' => $ancestors_w,
+            );
+          }
         }
       }

And yes, I did file a "issue" for this, with the Drupal people, http://drupal.org/node/309982 .