She can't resist

Mike was still confused with all the changes to his body and his senses, but some primal urge was rising inside him and guiding his actions. He reached out to caress Judy's cheek and cupped her jaw in his palm, forcing her to look into his eyes. "Relax Judy, nothing is wrong..." Her body began to lose the tension she had been in and she seized her struggles but there was still panic in her eyes. "But... You're naked in my room... And your dick? It's... It's..." She was suddenly uncertain of how to feel about this strange situation. She took another peek at his naked body, her eyes becoming fixated on his rock hard cock.

Feeling that he was now over some streshold, Mike pressed on, stepping closer to his sister and placing his hands on her hips. Judy leaned against Mike, her hands exploring his chest, his chiseled abs and finally resting on his dick. She took a deep breath, lost in thought and seemed to not even notice how she slowly slid a hand over his dick. Mike whispered in her ear "You can take a closer look if you want..." no sooner than the words have come out, Judy drops down to her knees and begins to admire her brother's cock. Caressing it, jerking it, finally leaning in to taste it... Judy lets out a long moan when the taste of her brother's cock finally hits her. She has to have more and soon she is deepthroating him and furiously rubbing her needy vagina with one hand. Mike now knows what to do and he grabs onto her head as his orgasm inches closer. "Fuck... I'm gonna cum in your mouth sis..." Judy doesn't stop and simply takes him as deep as she can, enjoying his cum filling her throat, there's so much of it that when she nearly chokes and pulls back, thick ropes of cum still land on her face and chest.

By now, neither of you can stop and you tear off Judy's clothes and move onto her bed. She eagerly spreads her legs and sighs in pleasure as her brother's cock enters her. With her feet raised on Mike's shoulders he begins to rail her and it doesn't take long for the both of them to cum again. This time though, more than just cum flood her insides as a parasite pours into her womb. Leaving Judy spasming on her bed, feeling orgasmic exstacy even as her DNA and brains are being altered by an alien being