You're having a bad time with your girlfriend so you turn to your sister for advice. She's always been there for you, there's no way this will be different. She's the best! You tell her of your issues of your girlfriend not giving you blowjobs EVER. "Ugh what?! That's so lame of her... What do you expect me to do anyway? Say 'hey girl, give my brother more head' lol". You didn't know what you wanted but all of a sudden, you're hard. She notices of course. You remind her of her reputation in high school, "Blow Job Queen".  She tries to hold back at first, but soon the Blow Job Queen is awakened again.