Can you imagine, finding the love of your life, building a relationship, planning your wedding, getting married, going on your honeymoon only to find out that the resemblance you found in each other wasn't a coincidence?
This is a sad strange story of twins separated at birth, meeting later in life and falling in love! They found out that they were twins after they were married! So sad and of course I know your thinking icky, right? Me too. I can only imagine what was going through their heads when someone said, "Your wife/husband is your twin, sorry your parents didn't mention this before." I think it's a good idea for adopted kids to search out their biological parents. There is valuable information to be found. This is not just an opinion, I know this as a fact. One of the important thing to know is what your families health issues, if any, are. Also, do you have a twin out there?
Just a thought, if you look too much like your fiance, don't marry them! lol!