So, in my books, I have astrology written in them ( very little because that is not what the books are about) Anyway- one character in the book, Venus, is a fairy nymph and she rules the element air. All the nymphs in the books are the fairies of 'lust' however she is actually one that has a little to do with love. She shows that for one scene in "Fairy Nymphs & The Demon Court" out in September. I am working on a new series that is a paranormal romance, with ancient Eygpt in parts of the story and I will add more astrology to this one as well.
Now in a man's birth chart the venus placement represents what he falls in love with and for a woman it represents how she acts when she is in love etc. Venus sign can also represent many other things like friendships etc., but this is how this placement represents love so to speak.
So when you find a man that dates one type of woman but marries another type, this makes sense. According to most astrologers, men marry by their moon sign, usually. That is why he may date one type of woman in his youth and marry a type totally different later.
So compatibility doesn't begin and end with a sun sign. There are so many other planet placements and also house placements that indicate that and many other aspects in a person's preferences.
To find out your venus sign, you need to find a venus sign chart and know the time you are born. Venus sign can only be either your sun sign or two signs past or two signs before your sun sign. For example, if you were born a Pisces, then your venus would either be a Pisces, Aries, Taurus, Aquarius, or Capricorn.