twenty eleven post type conditional

I want to include a file into normal single posts, but only for the normal posts. Is there a way I can add it in single.php without it effecting other posts types such as link, asides, quote etc?
<?php include_once('related.php'); ?> is what I’m adding.

The reason i want to exclude this from other post types is because adding it under
<?php get_template_part( 'content', 'single' ); ?> in single.php causes the comment area to overlap it (I tried clearing in css, adding a br tag and nothing seemed to work.
This only happens with quote, asides etc, and I can’t figure out how to keep it from doing that, so I figured I’d just add it to regular posts instead.

—Figured out an easy fix right after posting this.