Yes, it is VERY real...and a difficult obstacle for many people to overcome. It's nothing for you to feel ashamed of, despite the weirdness factor. It would be a good idea to read up on the subject a bit (just try googling "genetic sexual attraction" and you will find a few decent websites on the subject).
I first encountered this subject in Betty Jean Lifton's "Journey of the Adopted Self"...that's also a good resource.
Apparently this phenomenon tends to diminish over time as the reunion progresses and you establish a more grounded relationship.
Hope this helps
