This Is Why Married Couples Sometimes Look Like Siblings

Have you ever looked at a photo of you and your spouse and thought to yourself, “Gross… we kind of look like brother and sister”? Well, if you’ve ever wondered why your cheesy mugs look more like a picture of siblings than people who should be having sex, you’re not alone.

According to a new study published in PLOS Genetics, when two married people appear similar, it isn’t necessarily a coincidence, but may be related to the tendency to marry someone with the same ancestry. This trend can have important effects on the genetics of different populations, says Dr. Ronnie Sebro of the University of Pennsylvania and senior authors Josée Dupuis from the Boston University School of Public Health and Neil Risch from the University of California, San Francisco. The researchers in the study looked at the genomes of spouses from three generations of people and 879 spousal pairs from Framingham, Massachusetts, who were originally part of a 1948 heart health study.

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So, how exactly does this creepy phenomenon happen? Apparently, when most of the people studied got married, they picked significant others from their own community, and those people often had the same ancestry. Over time, the attraction to people like us, or from our communities, has created a similar genetic structure in the population.

Study participants with Northern European, Southern European and Ashkenazi ancestry were likely to select a spouse with similar ancestry, but each successive generation was less likely to choose a spouse with the same ancestry. Phew! So, props to all the dating apps out there helping us meet people who aren’t like us and don’t necessarily come from where we live. Keep branching out, single people!

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