It's biological and the nature of attraction. The same event happens in the animal kingdom. Subconsciously, you are naturally more attracted to those who have similar features as your own, whether it be similar facial features (eyes, nose, structure), similar height, similar weight, or even similar speech patterns and posture. This is why it is not uncommon to see many couples (both straight and gay) who look like they could be related. This particular site takes it to the extreme, however.
...Vin
