My brother is always thinking about tits, even when he's sleeping or awake. But even though she's a friend, I can't just let him experiment with her nipples without her consent, and I can't tell her that I work with nipple play... So, I, his sister who he can confide in without secrets, naturally become the target... I really rely on my sister when I'm in trouble... But it can't be helped, since we're siblings, and I always rely on my brother for help. I'll happily take off my shirt, or even my bra, for him!