..."My onesie, Duh! Where else would you be?" Jeff quickly put two and two together, and guessed that this meant she wasn't wearing underwear. "Well, alright!" He went over to the bed, behind her.
He kept an eye on her as she adjusted her bunny onesie, her little tail wiggling around, and then undoing the snap at the bottom, revealing her naked crotch. During this time, Jeff decided to take his clothes off. "Alright, I'm ready!"
He came closer and crawled in from behind. He easily noticed that it appeared bigger on the inside for him, due to the vore package. Once a good enough amount of him was in, she sealed the bottom back up, and sat down as his legs slid in. His sister, Amanda, giggled as she felt him moving around, eventually sitting at the bottom. He wasn't noticeable from the outside, which helped a bit.
His legs wrapped around her waist, and he tried to make sure the onesie's leg holes didn't reveal his own. He could feel her naked genitals with his feet, and his member hardened, which was pressed against her butt. "Jeff, that feels weird, what are you doing in there!" "Trying to get comfortable!"
She accepted the response, and stood up, running back to her room. Jeff slid down a bit; Not much, but enough to get his penis slightly lower, to where she sat on it upon sitting down. He could feel the soft lips of her genitals again, and wondered what all he could get away with...