I know what you mean. I think sometimes we find qualities/characteristics in other people that are familiar with ourselves and it makes it easier to talk and get to know them in the beginning and things like that. There's some kind of common ground that both people can relate to. And it just continues from there.
It's like if you have two people in front of you, one similar and one completely different, the one who is similar you can look at and pick up on certain things you notice and through six-degrees of separation you can get a sense of what their about before you even have a conversation with them. The one who is completely different raises more questions.
I think this is very true for a lot of people. I think people are attracted to what looks familiar. While there are many exceptions of couples who look nothing like each other, I see lots of couples that look like they could be cousins.
There has been research done on this... I think it's true that we tend to end up with people who are of the same level of attractiveness as we are. This doesn't necessarily have to be as specific as facial structure or similarities, but just overall attractiveness. And of course, it's not in all cases that this happens, but it's pretty rare (I think) to find couples that are huge amounts of attractiveness apart (again, that depends on who's looking).
My mom and step dad looked like they could be brother and sister. It was sick! Now that I think about it so do my husbands parents. A lot of my married friend look like they could be related so I guess it is probably true for lots of people. Then there are those of use who like our opposites. Me and my hubby look nothing a like. It has definitely made it interesting when our kids were born.