We see it as a quirky thing that so many married couples look more like siblings than lovers, and assume it's because they spend so much time together that their looks seem to merge. When they start to dress the same and pick up each others' mannerisms, we think of them as cute. But what about when their features are so similar they look like twins?

Elite Daily reports that thanks to a new medical study that literally no one asked for, we know the weird (and frankly grim) reason why. I hope you're sitting comfortably, especially if you share some facial features with your partner. It's because married couples genuinely could have similar genes. Yup.

Researchers at universities in Pennsylvania, California and Boston found people are most likely to marry someone with the same ancestry. Before the days of easy, cheap travel and online dating, humans didn't really have any choice but to hook up (and reproduce) with people in their local community.

Published in PLOS Genetics, the study found the pattern of white couples marrying and having children within that area repeated over time. Basically, they were keeping it in the gene pool for generations.

Apparently, people of Northern European, Southern European and Ashkenazi Jewish descent were the most likely to marry someone with the same genetic background as themselves. Fortunately, they studied families over three generations and found this tendency to pair off with someone who shares our ancestry has declined over time.

If we could just all just make sure this doesn't happen by looking a bit further afield when choosing someone to spawn offspring with, that'd be great thanks.

From: Cosmopolitan UK