I'm trying to implement creation of child nodes programmatically in hook_submit when creating parent nodes according to the parent node field value. Here is the idea. Parent node: field_stages (unlimited count). I want to create new "stage" nodes when I've added new parent node and save a reference to these child nodes in parent, although the references should not be editable and visible in add/edit form and node view. How it can be implemented in drupal?

I'm trying to programmatically create child nodes according to a parent node's field value.

When a node is created, a reference to these child nodes is saved in the parent node, although the references should not be editable and visible in the edit form and when the node is viewed. 

How can I implement this?