Still asleep.

Her eyes stayed shut, but you could feel her cock sucking you in even more. "Alice please! Your dick is sucking me in! Help!"

Your sister smiled with her eyes still closed, "Ok Will... I'll help and suck your cock..."

What?

Before you could even fully comprehend what she had said you could see her mouth open and approach her cock.

You were engulfed in total blackness as her mouth wrapped around her own giant cock. At first you could just hear and feel her breath as she held it in her mouth, but then you feel her mouth suck on it softly. After a few more soft sucks she started sucking harder and thrusting her head. You felt her cock throbbing around you, but just before she came she pulled off with an audible pop and said, "Mmmm Will your cock is so good... I've wanted to swallow your cum for so long.... give it to me!"

Oh no. "Alice sto-!" You were cut off as she took the full length into her throat and held it there. Her dick throbbed around you painfully as the tension built. You could hear her moaning and gulping hungrily in anticipation.

The last thing you felt was a rush of thick liquid behind you as she came, and sent you gliding down her throat as she swalled you and every last drop of her own cum.