i do believe this happens, but EEW. as far as my big bro is concerned, he is my big bro and that is IT. i just kinda thought your big bro/sis whatever was chosen b/c they fit that specific criteria....and being attracted to them in any way doesn't really fit in there anywhere for me.....and i'm in kentucky!
however, my BB did inform me drunk one night that he was "in love" with me.....and i think i was trauamatized for life.
(ilovemyglo, you're trauamatized now, too, huh?!)