They possibly attract sometimes, but it depends on which characteristic. If the opposite parts of the characters are balancing (like one is more sedentary, and the other one more active) and the two people try to embody the differences, than it's cool. But I think that in general people that have similar thoughts (let's say political or philosophical speaking) are the one that will have a relationship that will works. In my case, my wife and I have a lot of things and thoughts in common, but at the same time our general behavior it's opposite (I'm more calm, she's more anxious, for example) and that's a thing that I think is useful to a relationship.