Time for a position change.

Crystal moves her hands to your butt and grunts and as she suddenly stands up, forcing you to wrap your arms and legs around her to avoid falling. You are astonished by your sister's strength as she starts to fuck you again, using her grip on your ass to guide you up and down her cock. You are completely at her mercy now and groan in pleasure as she uses you as her sex toy, your only purpose to pleasure her superior girl-cock. You hug her tightly against you, her breasts flattened against your chest, and try to use what leverage you can find to fuck her even harder.

After several minutes of this, Crystal walks toward Sarah's bed, her cock fully implanted in your ass. She leans you back toward the bed, slipping a pillow under your ass to keep it at the right level, and places your legs over her shoulders. As you lay back on the bed, she starts pounding you again, your hole tighter on her cock now with your legs squeezed together. The stimulation on your prostate is too much for you and you climax, your semen spilling over your stomach. Surprisingly, your cock remains hard as your sister continues you fuck you mercilessly.

You feel the bed shift as Sarah gets on and, facing your crotch, straddles your head, her erect cock hanging above your mouth. Without hesitation, you open wide and accept her member as she lowers herself down on you. You feel it press against the back of your throat, but due to the angle, it won't go down further, no matter how hard she pushes. Seeing her predicament, Crystal pauses her activity and grabs another pillow, lifting up your back and placing it under your shoulders, causing your head to tilt back and your throat to open up. She goes back to fucking your ass with a chuckle as Sarah pushes her cock all the way down your throat, her nut suck pressed against your nose filling your nostrils with her musky scent.

All three of you are now moaning in pleasure as your sisters furiously fuck you, your own moans muffled by the cock in your throat. A wonderfully warm, wet feeling envelopes your dick as Sarah leans forward and takes it into her mouth, continuing to fuck you as she bobs her head up and down on it.

Time seems to stand still as you are overwhelmed with pleasure. You don't know how long the three of you continue like that before you here Crystal shout out a warning: "I'm cumming!" You feel a warmth fill your ass as she dumps her load deep inside you. At the same time, Sarah starts to cum down your throat, triggering your own ejaculation into her mouth. You can't believe how much semen Sarah pumps into your stomach considering she's already dumped two loads inside you.

Finally, you are all finished and your sisters get off you, stepping back from the bed.

"Yuck, that's gross," Sarah complains as she spits your semen out of her mouth.

"Yeah, boys' cum can be pretty bitter," Crystal informs her. "Why did you take his dick in your mouth?"

"I don't know," Sarah answers. "I guess I just got carried away in the moment."

"Well, girls' cum tastes a lot sweeter than boys'. Next time you should cum in his mouth so he can taste and enjoy it, rather than shooting it straight into his stomach. Isn't that right, Dougie?" she asks you.

You smile an affirmation and close your eyes in satisfaction. You've never felt so content in your life, laying there on the bed exhausted, your hand on your bloated stomach. You feel like you've discovered your life's purpose -- to be a sex toy for your sisters, used and filled whenever they have the urge.