Sharing The Bed With Your Sister

You and your family are on spring break vacation, and as your sister tries to claim the king bed as her own, she discovers that your Mom didn't get you two different beds and you will have to share a bed. She is pissed, telling you to mind your space and leave her the fuck alone. However, early in the morning she nuzzles her ass against your cock, and when she awakes, she has a second of shock and confusion, but is overtaken by her arousal, taking your cock and easing it into her pussy. You wake, finding her grinding back on it, and you thrust back in return. She tells you to pull out, but as you bend her over into doggy, you can't help but take her pussy as your own, eventually filling it up, risking impregnating your own sister. She tells you to go grab a plan b and a thing of condoms, since you'll be sharing a bed all week and you suck at pulling out...