I have seen many couples who look like siblings. Once even came across a book on the subject in the library. Whether people like themselves, or want somebody looking like their opposite-sex parent, or just look for familiarity, there definitely is something to it.
I have a very serious problem with this issue...
I pretty much only find men looking like me (or Dad...) attractive. The coloring is not that important, but the shape of the face is. I also have a dimple and like one very much, even if it's on the chin. The eyes can be different, the nose can be somewhat different, but the lips have to be similar. I have never liked anybody (men or women) with thin lips. Those people look mean and often ARE. I'd have no desire to kiss such lips.
Being foreign-born and living in a city without a diverse population makes finding somebody appealing to me extremely hard. I have kind of a Mediterranean look and I just can't see myself with a guy with English/Irish looks. A different race is almost out of the question. While I occasionally may find a Black man attractive, it would be despite his skin color, not because of it. He may have some of the features I find attractive.
Unfortunately, the problem doesn't go away with age. As a matter of fact, it gets worse. Age may have less to do with it, though. My Dad being deceased may have more to do with it. My last ex-husband looked very much like us. I didn't meet him by chance. At the time I was looking for trouble (less than 3 months after Dad's death) and sure enough found it.
I wish I weren't wired this way, but I am, and there isn't a whole lot I can do about it. I'm perfectly aware of the reasons behind many of my not so wise decisions and yet just can't help it... It's a very bad situation because knowing I'm attracted to very few men makes me cut a lot more slack than I should to those who do fit the bill, which leads to disappointments and tragedies later on. I may even realize it's all wrong at the time I'm doing it and still can't stop myself.
There is one exception, though. If somebody stimulates my mind and inspires my imagination without my knowing what he looks like, I can be a lot more accepting and flexible once I find out. Guess forum crushes and profiles with no pictures are just the thing for me!
On the bright side, I'm certainly not alone:
http://www.wired.com/wiredscience/2010/07/incest-taboo/