lucy24 - 8:16 pm on Jul 3, 2013 (gmt 0)
Are they registered under the same domain registrant name?
See parallel thread about advisability or otherwise of keeping whois information publicly available.
I have never seen 3 identical websites ranking on page 1
You're kidding, right? I've seen the same page in 1, 2, 3 position. Different URLs, but a human can get from one to another by re-sorting or by clicking a "more info" box that adds to existing page content without changing anything above-the-fold.