She's not some random girl, she's your friends sister, you need to clue him in.. Pull the "you're like a little sister to me" card if you have to.
A year ago I met some new friends who have a shop next to mine, initially i was friends with one of the brothers, his older sister liked me, they
I'm in love with my best friend's younger sister. I've known her since I've known my best friend and always been attracted to her but never done
I've been texting my mates sister (he doesn't know) and I wanna meet. my best friend is going out with my little sister (srs) and its' not weird at