Have you ever seen those couples that could pass for brother and sister? Not in the way they act but more about how they look. Look to your own spouse, do they kind of look like you? Weird to think about, but you might see it more than you think.

If you see this all the time, you aren't alone. Many researchers are studying whether people are attracted to people that look like them, and there are some interesting theories about it.

You have probably heard of the theory that people are attracted to those that look like their parents. A very creepy theory, but it makes sense when you think about it. Sigmond Freud coined this theory as the Oedipus Complex, and his reasoning behind it was, that people subconsciously yearn for a time when their parent took care of them, so we look for that in a spouse.

Being attracted to people that look like ourselves could also be part of this theory. Being attracted to our parents is sort of like being attracted to ourselves, because we share the same genetics.

With these two similar theories, researchers are now looking into the theory that we are attracted to people who share DNA similar to our own.

They are calling it genetic assortative mating, and it means that we look for people with the same body type, ethnic background, or other physical traits as us.

In one study, a picture of a stranger was morphed with a picture of a participant or a picture of another stranger. When subjects were asked to rate the portrayed people for attractiveness, they usually picked the people who were an amalgamation of a stranger and themselves.

This next study is one that I have never heard of and one that scares me just a little bit...

Another very weird theory was discussed, and it was that long-term couples begin to look like each other the longer they've been together. Social psychologist Robert Zajonic was one of the first to point out that long-term couples started to take on each other's facial expressions the longer they were together.

In 1987, he released a study of photographs of couples from after they first met and when they had been married for 25 years.

From the results of his study, which showed the couples' faces looking more and more like each other as the years passed, Zajonic theorized that couples who live together long enough would mimic each other's facial expressions and that would actually change the physical structure of their faces.

Why this happens is unknown and incredibly creepy to me.

There are a lot of different theories and studies about being attracted to people that look like us, but there isn't much of an answer as to why this happens. This information tells us one thing, that we're trying our best to date ourselves, and apparently after a long enough relationship, our partners will look like us.