WordPress at a glance
filter is not described

parent_post_rel_link filter-hook . WP 1.0

Usage

add_filter( 'parent_post_rel_link', 'filter_function_name_8130' );
function filter_function_name_8130( $link ){
	// filter...

	return $link;
}
$link
-

Where the hook is called

get_parent_post_rel_link()
parent_post_rel_link
wp-includes/deprecated.php 2770
return apply_filters( "parent_post_rel_link", $link );

Where the hook is used (in WP core)

Does not used.