Maybe your psyche is projecting an ideal version on him...because a part of you likes him but know he's not right for you. I think our unconscious often tries to solve issues we have with people; things we wish they would tell us, or how we precieve their attitude towards us for our opinions of them to be confirmed and valified.Who knows maybe you do have an astral relationship with him? Maybe plan ahead and try to practice what you want to say to him (before bed) so you have a better chance in your dreams..if we want this to stop for example I mean.
Some other food for thought; you probably know that being semi naked in a dream and shower has to do with self-image and cleansing of self. Meanwhile your dreaming of these other guys who sound like they have a very masked macho ego, and this old love interest had called you a sister, but kissed you once. Sounds like you may be trying to get to the bottom of who this people really are. They may have attributes that you share and dislike or wish to incorporate. Also consider the sister comment as a possibility that your unconscious super-ego has guilt for your attraction and wants to work it out on a level you can accept.
Some people also believe that the characters in our dreams are ALL just other sides of ourself.
Idk...hopefully some of that helps you draw your own conclusions..good luck!