You want her sister

"I want you, Carrie," You say confidently. "There is just no other girl like you. Except maybe..."

"Maybe what?" Carrie asks looking at you with hope as if it was about her dream and not yours.

"No. This is a stupid idea. Forget about it" You try to change the subject but if your girlfriend has any flaws then it is stubbornness.

"No. No. Tell me. You know I hate any secrets between us"

"Well," You feel like the largest pervert in the universe "Your sister is like a younger version of you and I had some fantasies of this kind starring her. But I, of course, won't **** Cassidy for real."

"Why not? You want to," Carries smiles in a rather nasty way"Her and you... That would look so hot. We only need to plan a way to get her in your clutches"

"You can't be serious" You expected to see her angry, even disgusted but she is definitely cool about it.

"Why? I love her and everything. But I love you more. If that requires some suffering for her, I am willing to go this route" She lands a wet sloppy kiss on your lips "I am ready to give you everything. Everything. Just say me how and I'll get her cunt for you to ravage"

It is now when you understand that it is a very real possibility and you can act on your deepest darkest fantasies should you truly wish it.