Do as you're told

You take the dildo from Gwen. She climbs onto the bed with you and straddles you, leaning down like she's ready to kiss you. She says, "Put it in me."

You reach down and line the fake dick up with your sister's hole as best you can, and push it upward into her. She grasps your head on either side and kisses you deeply. You suddenly feel another mouth, but this one on your pussy. Amy starts licking you out as you shove the dildo into and out of your sister. You fuck her with the toy until you feel yourself approaching climax, when you start moaning into your sister's mouth. You feel your sister push down hard on the dildo, and pushes it all the way down until she's sitting on your belly with the dildo embedded completely inside of her, and the two of you cum almost at the same time.

You feel Amy stop licking you, and your sister finally breaks the kiss as you both come down from your orgasmic bliss. You look down to see Amy lick her lips and say, "Tastes like Lauren just got fucked before coming in here!"

"What?" your sister responds, her face going ghostly white.

"Don't worry, Gwen, I just ate all of your brother's cum out of her so that you wouldn't have to."

"Nonono, that's not it." Gwen turns to you and asks, "Did you just fuck John before coming in here?" Unsure of what to say or do, you freeze. "Well, did you?" she asks again.

Considering you did just get fucked beforehand, you meekly nod.

"Fuck!" Gwen screams, and jumps up from you, the dildo falling from her pussy onto her bed. She rushes out to your shared bathroom. "You just fucked me pregnant with my brothers cum using my own fucking dildo!"

Thinking back to your recent fuck session, you say, "But we used a condom!"

Amy shakes her head, and says, "You should check your condoms for holes, missy! It certainly doesn't taste like you used one."