This can't be done with Wordpress posts because their post_parent
field cannot be set using the Wordpress admin interface as it can for pages.
However, given that both content types use the same database table and share many fields, it should be possible to write a plugin to allow the post_parent
field to be set for posts (I can't find any existing plugins that do this), you could then retrieve a post's child posts using the get_children
function.
You'd need to add a metabox to the post edit page to provide a form for selecting the post parent, and then hook into the save_post
action to save the chosen post to the post_parent
field. See this example of how to add a metabox and hook into the save_post
action: http://codex.wordpress.org/Function_Reference/add_meta_box#Example