Automatically set post_parent value

You can do that easily using save_post hook like so:

function set_post_parent_on_save($post_id) {
    // If this is just a revision, don't do anything
    if ( wp_is_post_revision( $post_id ) )
        return;

    // Check if it is a post
    if ( 'post' == get_post_type( $post_id ) ) {
        // unhook this function so it doesn't loop infinitely
        remove_action( 'save_post', 'set_post_parent_on_save' );

        // update the post, which calls save_post again
        wp_update_post( array(
            'ID' => $post_id,
            'post_parent' => 88 // <- or whatever the parent should be
        ) );

        // re-hook this function
        add_action( 'save_post', 'set_post_parent_on_save' );
    }
}
add_action( 'save_post', 'set_post_parent_on_save' );

But… It isn’t best idea to do this this way and I would rather take a look at the way the breadcrumbs are generated and tried to fix it, so it works properly.