The related: method doesn’t work anymore. Which means you have to check the links:http://www.thesiteyouarechecking.com and verify whether those sites actually do link to the site in question. You should generally click on the “cached” version of the pages. View source and search for your URL in the body of the page.
If find that the sites do not link to the URL – you are very likely looking at spoofed pagerank.