<human>: He and I have been friends for about 10 years now and we're in our early 20s. His sister is a few years younger than us. I get along well with their family, they're practically family to me, and that's probably why I'm not sure what to do about this. I'm not afraid of being rejected and I don't care if it makes things weird between me and her... I just don't want to mess things up between me and the rest of them.

Do I give up while I'm ahead and leave things the way they are? Should I just go for it and ask her out? I've been seriously considering talking to her brother about it first, how does that idea sound? Feel free to ask me anything, I'll be answering in a way that I feel would make it impossible to figure out who anyone involved is, just in case. I really need some help here, this has been on my mind for a while.

Can you condense the text into a few key points?
<bot>: I'm in love with my best friend's younger sister and I don't know if I should go for it or not.