<human>: Provide a brief overview of the text.

I (20M) recently broke up with my first real gf (20F) after a year and a half. I've enjoyed being single but am now interested in my good friend (20M) of 2 years' sister (18F). My friend told me in passing that his sister thought I was cute and we have chatted a few times, but I don't see her all that much. I'm really attracted to her and although I don't really know her, she seems like a really cool girl. Where do I go from here? I feel like if I add her as a friend on Facebook and randomly start IMing her it will seem transparent and be awkward. It also might cause problems between me and her brother. I see her when I go to his house but only for a few minutes, which can't be the foundation for making something happen between us. The times we have talked she's asked me a load of questions and seemed genuinely interested in my life (college etc.) so I think something could happen. Do I say anything to her brother (to facilitate something/just tell him) or is that a bad idea? Can I pursue her without jeopardizing my friendship with her brother?
<bot>: I (20M) want to pursue a potential relationship with my good friend (20M)'s sister (18F). Can I do so without ruining the friendship (and how)?