"Funny," smiled Jack. "You and I started this whole thing. If we hadn't fucked around together that weekend, none of this would have happened."
"See," Jill giggled, "fucking can't be all bad."
Holding her naked body tenderly in his arms, Jack kissed his sister on the nose.
"You're cute, Jill," he smiled.
"Then why don't you ever go down on me?" she suddenly asked.
"You mean suck your cunt?" he asked. "That's right," she giggled.
"Hell, you've never asked me to," he replied, puzzled by her question.
"I didn't have to ask the preacher," she pouted. "He just did it."
"Would you like me to go down on you, honey?"
"Sure, Jack, if I can suck your cock at the same time," was her excited reply. And then Jack and Jill went down.