We have all one (or more) good friends with cute sisters, and I (as many others I'm sure) would never consider affecting the friendship for some quick fun (a relationship is a different story obviously). I realized yesterday when I was hanging out with my friend and her sis that I was treating her in the exact way that I should treat all other girls I'm interested in. By not putting her on a pedestal, by slightly ignoring her when she starts dancing with me but keeping the good vibe and a smile once in a while to acknowledge her presence, minimize staring, almost treat her like a bro in the sense that I would tell her random funny comments that would come to mind and we'd laugh etc. She almost felt like I am have completely taken her out off of my equation (of romance/hook ups) and that' seems to be an attractive vibe, because then she feels (perhaps subconsciously) that she has to qualify herself....weird shit.