Automatic links

I'm creating a Drupal site about boardgames, and my data demands a parent-children structure --- some boardgames have expansions. Now, I've created a content type for boardgames, and another one for expansions; in the fields for the expansions, there is a field that points to the parent game. But is it possible to automatically update the parent game node to indicate that there is a child node now? In other words, how can I traverse the tree from the root to the branches?