You see, people tend to like someone who has something in common with themselves. That's why primordialism, racism, and any form of in-group favoritism are still relevant topics even until now. Apparently, when it comes to physical appeareance, this favoritism is also likely to happen.
You ask what's the evidence?
A study had been conducted in order to check this phenomenon. A group of people were asked to choose pictures in which there were faces of persons from the opposite sex. They were told to pick out the faces they liked the best (and maybe would like to go on a date with). Actually, one of the pictures was a modification of their own faces, how it might look in different sex. Yeah, the result shows that people are highly interested in their own picture.
*oh, narcissism...
So, if you meet people who said you look like your romantic partner, don't rush into conclusion that you guys are match made in heaven. Look-alike may not because you are soulmates, try the other way around... maybe you choose him/her to be your soulmate because you both look alike.
