Should I ask out my friend who's a girl little sister ?

[Anna]

Well you could first ask your friend if her sister likes you back, then you won't be ruining a friendship if something goes wrong. Also, what if your friend likes you? have you talked to her about whether it's okay or not to ask out her sister?

But if you really want to ask her out, i would personally do it in person rather than over facebookor text. Next time you all hang out, when youre all about to go home, ask your friend to leave and give you a chance to be able with her sister. Then just say like "Hey, so i was wondering if you wanna go _____ just the tw of us sometime?"

Good Luck!