Greedy lust

Whatever else Matt had noticed while inside his mother's body held nothing to the shock at seeing his twin sister's desire for their own father. Apparently they had been fucking for some time, and despite his sister's pure demeanor, Matt had seen another side to the girl, one that he doubted her infrequent boyfriends had ever seen.

He got up from the bed, walking over to the closed door and opened it ever so slightly. He watched as his mom went back down the stairs, verifying his feeling that the situation had not been in error. The woman knew what had been happening in the bedroom, and had no objections to it.

Sudden light washed over the hallway as Matt's dad left his sister's room, buckling his belt as he headed toward the bathroom, only to be cut off as the door closed behind him. Matt snuck out of his room, closing his own door behind him as he walked toward his sister's room.

His dad had closed the door all the way, apparently having neglected to do so in his haste to fuck his daughter, so Matt no longer had the handy gap to look into. Grasping the handle gently, he slowly turned it until the light returned.

Lily was no longer standing in front of her desk. She was also not sitting at the desk, which is what Matt had half expected. He kept opening the door until he caught sight of her. His twin sister lay on the bed, her eyes closed tight as her right hand moved between her legs, her left massaging her breast as she masturbated. Matt's cock sprang to life, and after he stepped into the room and quietly closing the door, he stepped toward his sister's bed.

He watched Lily, noting how her thumb rubbed her clit while the first two fingers slid in and out of her shaved pussy, noting how her teeth bit into her lower lip with surprising ****. Matt wondered how she wasn't biting through the lip. Then her left hand stopped massaging her breast to pulling on her nipple, twisting it with apparent pleasure as her body started trembling.

Matt couldn't take any more, and he stepped forward, his thumbs hooking into the waistband of his shorts and pushing down, his hard cock springing from the waistband to point at his twin sister.

Lily's eyes opened, then her mouth as she exclaimed, "MATT!", her voice both startled and...