I agree with this statement but it can be extended to friends too. My mom has told me that people have stated that my dad and her look alike. My mom also told me that one of her closest friends stated that people often think she and her husband are siblings.
In my personal experience, an eerie thing happened. It was with my closest and dearest friend. I took a picture with her and thought a nothing of it. It was until afterwards when I (and others) look at a particular picture and we looked like blood sisters. Mine you we don't look alike at all. But in this picture we looked physically/facially alike. We were simply just smiling btw. It was like we unconsciously and physically channeled and brought the essence of each other and ourselves out and turned it into a whole. This was then communicated into the picture and this picture captured our likeness and our relationship.
This never happened before and hasn't happened since, but I thought it was strange and magical. Also take a look at this picture of Pop Star, Lady Gaga and Donatella Versace .below... eerie the resemblance. Not sure of their relationship, but in my opinion they look very similar, like they are related (subtract the wigs and the makeup). Its the expression and how they vibe off each other.
I think whether married, in love, close friends, or otherwise; people have the ability to channel other people's energy, connection and spirits. And sometimes this energy and connection can be seen with the naked eye. Great question btw!!