My Ex-Girlfriend Is Basically My Twin — Is That Weird?

In the neighbourhood where I used to live, there was a friendly crossing guard who protected pedestrians as they crossed the street. Every morning, without fail, she'd spot my roommate Katie and me walking together. "Good morning, twins!" she'd shout. We'd awkwardly wave and smile, but there was one little problem: Katie isn't my twin. She's my best friend, and at the time, she was my girlfriend.

It'd be easy to laugh this off if our crossing guard was the only person who made this mistake, but she isn't. Strangers at the grocery store, strangers at the mall, strangers on the subway, and strangers who pass us on the street have all stopped to ask us if we're twins.

At first, we rejected the idea that we look alike (Katie still does — "I don't look like you. You're ugly," she joked when I told her I'd be writing this story). It seemed like something that happened because we're gay. Of course people would immediately think that two women who were holding hands on the street were sisters and not girlfriends. It's not an unreasonable thought; queer women are commonly mistaken for sisters, sometimes even when they're of different races. In our straight-focused society, people who see affection between women often assume sisterhood or friendship before they assume romance. But when people kept asking us if we were twins, even after we broke up, I had to face the truth: Katie and I actually do look alike.

I can take some consolation in knowing that we weren't the only clone couple out there. Dating someone who looks just like you is such a widespread phenomenon among gay men that it sparked a Tumblr page called Boyfriend Twins. While I like to think that there are several noticeable differences between Katie and me (her eyes are brown and mine are green), some of the couples on that Tumblr look like carbon copies of each other.

It's not just a thing among LGBTQ+ couples, either. Plenty of straight, married couples look alike, too. But what's really at play here? Is it an inherent attraction to people who look like you? A consequence of living in a town where everyone looks the same? Or the weird way people eventually morph into their partners? Science has arguments for all of these possibilities.

Sigmund Freud's famed Oedipus Complex theory claims that people will be attracted to someone who looks like their opposite-sex parent (ignoring same-sex attraction, of course), because they subconsciously yearn for a time when their parent took care of them. Being attracted to people who look like our parents basically means the same as being attracted to people who look like us — because that's how genetics works — and further research supports the idea that we're interested in people who share DNA similar to our own.

It's called "genetic assortative mating," and essentially it means that people are subconsciously on the lookout for someone who has a similar body type, ethnic background, or other physical traits. Although these studies indicate that people often do end up with someone who looks like them, they don't necessarily explain why.

That answer might come from other theories, like the idea that we learn who to be attracted to from the communities in which we grow up. R. Chris Fraley, PhD, a psychologist who studies romantic attachment, told Slate that people who grow up in communities that aren't racially diverse are more likely to start relationships with people who have similar physical characteristics than people who grow up in racially diverse communities.

It makes sense. If you grew up seeing only one type of person, you might find that type of person attractive. But there are still some holes in this explanation. Why, for instance, would body type matter? Or hair colour? Or the way you and your partner dress?

According to one of my coworkers, what really makes Katie and I look alike is our shared personal style — our clothes, our glasses, and our makeup choices. It's not necessarily that we physically look the same — although we are both white and short and have a similar body type — but that we've kind of morphed into each other.

Although I use the word "morph" lightly in my case, some scientists believe that couples who've been together for a long time literally start to morph into each other. That phenomenon is called convergence.

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 when 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 theorised 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.

While I'm sceptical about saying that my six years with Katie have fundamentally changed the structure of my face, they've definitely changed the way I dress and the makeup I choose to wear. The great thing about having a girlfriend (and now ex-girlfriend/roommate) who wears the same size as you, is that your closet doubles. On any given day, I'm more likely to be wearing Katie's clothes than my own. Katie taught me how to do my makeup, too. Before her, I could barely put on eyeliner, and now I have a lipstick in every possible shade. To say Katie influenced my appearance would be an understatement.

So do any of these theories explain why Katie and I were attracted to each other? I have no idea, but it doesn't really matter. My not-twin is the best friend I've ever had, so I've decided not to let the questions bother me anymore. At least until the next time someone asks.