I still feel they are perhaps aspects of the same person, that is, aspects of yourself. I must admit that I feel almost like this guy is not quite a dream character. Usually the people we dream about are representative somehow, and often represent aspects of ourself. I feel almost as though this guy IS part of you somehow. Quite REAL, as if one day you'll find him walking down the street and recognize him as part of yourself, like a twin or "brother" as you mention.
This is just what I felt intuitively from your words, which are very powerful.
The fact that one is dark-haired, one is blond, tall, short etc. I would just attribute to different representational aspects. What do these qualities mean to you?