You tell her no

"Sarah, I can't ask you to do that" you answer. "I don't feel right about sharing James with you, and Robert is someone I have to deal with on my own. I created this mess, I have to get myself out of it, now matter what happens. What you're doing is offering me a license to cheat on James. That has consequences in and of itself that I don't think I can handle. Listen, I love you, and I appreciate what you're trying to do, but my conscience is guilty enough without what might happen to you being a part of it. What if it goes farther than just a blow job?"

"Then it's just sex, isn't it?" replies Sarah. "It would give you the freedom to have sex with Robert."

You stand up and start pacing the floor, rubbing your forehead. "But I really don't want that to happen! Can't you see? That's why your offer is so dangerous." You sit down next to her, and hold her hand in yours. "I love you, Sis. I couldn't ask you to do something like that."

"It's all right, I understand how you feel" says Sarah. "I love you, too, and I just wanted to help you, and protect you. You're my baby sister, after all. I've always looked out for you." Then she kisses you. But it's not a typical sisterly kind of kiss. This one is hot and steamy, like a lover. "I love you, Katherine. I always have, and I lost the better part of me the day you got married."

You're not sure how to take the kiss, or the startling revelation you've just been handed. Your own sister is in love with you? All you can do is sit there, wide eyed, blinking at her. You love her too, but is it the same kind of love she has for you? "I'm not sure what to say about all of this, Sarah. I know I love you , too, but I don't know if it's the same kind of love. A part of me wishes you would have told me this before I got married."

Tears start rolling down Sarah's cheeks. "I wanted to tell you, but you seemed so happy. I didn't want to ruin your happiness. And now, here you are, all miserable because of some schoolboy coming on to you. I guess the only way I thought I could have you, and to be a part of you was to share James with you. That's why I made you the offer. We used to hang out together, and share everything together, and I still want to do that with you. I love you so much." She caresses your face with a touch of her hand. It suddenly becomes an electrifying touch that makes you feel weak inside.

"Your makeup's running" you say as you wipe away her tears. But it soon turns into a caress of your own, and soon you're caressing each other. You can finally stand no more. "Sarah, will you kiss me again?"