If you believe the research of scientists, which Prof Robert Winston did a fantastic TV show about a few years ago, it is that nature has decided that your genes are a perfect match with which to produce strong, healthy offspring, and thus ensure the furthering of your genetic lines. Basically he was suggesting that we are so civilised now, and so "developed" that we tend to forget the very successful mechanisms that evolution has given us and are still very important in what we call "chemistry".
Pheromones, physical attributes, voice, smell, etc... will all play a part. I find that with my partner, I even love the way she smells... When we've had the weekend together, I almost find myself rolling around on the bed like a cat in a bed of catnip.
Those are all very physical attributes rather than mental ones... Nature doesn't really care about mental attributes that much since they aren't critical in breeding, but as we have learned to become more civilised, they have become important to us. We have developed into complex social beings rather than animals, so now we also find certain mental attributes attractive.
Most of the above is all very amateur psychology ! I'm fascinated by it, but my recall of the TV series and my lack of reading will no doubt make a professional gnash their teeth. I think the overall gist is correct though. :)
Don't overthink it. You've been lucky ! Go nuts ! :) With luck the mental connection will be as strong as the physical one.
RLD.