"That's disgusting! I'm your brother -- how could you think about me like that? I would never do anything sexual with you. That really grosses me out!"
Sarah's jaw drops and her eyes go wide in shock at your outburst, before she runs out of her room crying.
You feel bad about having spoken so harshly to your sister. You aren't really that angry -- it was mostly your shock at discovering that your little sister has sexual fantasies about you that prompted you to respond as you did. There's even a suggestion at the back of your mind that your over-reaction was triggered by disgust at yourself for getting aroused by her earlier, but you try to ignore that.
You briefly consider going after your sister to apologize, but decide against it. You may have gotten a little carried away, but what she was suggesting is still completely inappropriate. Feeling satisfied with this rationalization, you return to your room to start on your homework.
Before you've even gotten your books out, however, your mother comes storming into your room, your sobbing sister behind her.
"What did you say to your sister?" your mom demands. "She's so upset -- all I can get out of her is that you yelled at her. Is this true?"
"Yes, but..."
"But what?"
"She was being really gross. She wanted..."
"What did she want?"
You turn red in embarrassment, too uncomfortable to explain it to your mom, and look over at your sister's playgirl, still lying on the floor. You mom looks at you quizzically, walks over to the magazine, and picks it up. She sighs in understanding when she opens it up and sees what's inside.
"Doug, I'm disappointed in you."
"What?" You weren't expecting that response at all.
"Your sister is going through a hard time right now. You wouldn't understand because you're a guy. You see, when a girl goes through puberty, they have far more hormones going through their body than boys do when they go through puberty. Masturbating may have been enough for you, but Sarah needs far more stimulation than that to deal with it. It's perfectly natural for her feel that way about you -- she loves you."
"But, mom, I'm her brother," you complain.
"So? You should feel honored that she fantasizes about you. Now apologize to your sister."
You do feel bad about the way you treated her. You’re uncomfortable about the situation, but that's no excuse to be mean to her. Sarah has stopped sobbing by this point and merely sniffles from time to time, her eyes red. She looks up at your hopefully.
"I'm sorry, Sarah."
"Do you accept your brother's apology?" your mom asks your sister. She smiles and nods her head.
"Great! Now that that's cleared up, why don't you give your sister a blowjob, Doug."
"What?!?" You can't believe you heard what your mom just said.
"Didn't you hear anything I told you?" your mom asks you in exasperation. "Your sister needs your help. Masturbating isn't enough -- she needs more direct stimulation. You're her brother and she loves you. It's your duty to help her. Don't you love her?"
"Well, yes, of course, but..."
"But what?"