Mazel Tov!
Firstly, no it’s not a “real” thing, it just happens that way sometimes. If anything, I have heard that a kallah might look like a chosson’s sister or relative sometimes, because he is attracted to what he is used to (or vice versa). A lot of people think I look like one of my sister’s-in-law, and my married sister has the same story. But it has no real basis or anything, so don’t stress over it!
Enjoy your engagement- it’s a very special time!