A function for WordPress. It returns true if comment is a parent and false it comment is a child.

aa_comment_parent.php

<?php 
/**
 * Comment Parent Check
 * 
 * Returns true if comment is a parent comment
 * and false if it is child comment
 * 
 */
 
function aa_comment_parent($aa_comment_id) {
  $aa_comment = get_comment($aa_comment_id);
  $aa_comment_parent_id = $aa_comment->comment_parent;
  
  if ( $aa_comment_parent_id == 0 ) : return true; else : return false; endif;
}