Mom and Dad went out to dinner and left your older sister home to take care of you. She's her usual bitchy self, and complaining about everything, until you tell her she has to help you cum. Your balls are so swollen and she makes you wait while she calls Mom to find out how to handle this. She strokes your cock, teases you with her big natural tits, and makes you cum all over her, before finding out that she's suddenly pregnant, and carrying your baby before your cum even dries