Follow her

Matt stood there for a second, not sure what to do, in a pleasant post-cumming haze. He grabbed his water and gulped it down, but it did nothing to clear his head. After a minute, he shook himself loose and slowly walked after her.

He could hear his mom in the living room complaining to his dad about how Clair shouldn't be doing 'subservient' things with a man, even her brother. As he began to climb the main steps, he heard a moan coming from the living room. He turned to look, then quickly turned back and rushed the rest of the way up the stairs. In that brief second, he had witnessed his mom sitting in his dad's lap, fully clothed, the two of them still talking about Clair and him, but her on his lap being bounced energetically, if only slightly, by her husband; even he could tell they were clearly having sex. Like most people, he preferred not to think of his parents like that, and he knew for damn sure that they had never done it in the living room, at least not as long as he had been alive and certainly not with a house full of people. The parents he knew would have been mortified at the very suggestion...

Something was nagging at Matt, but he couldn't put his finger on it.

The upstairs arrangement was based on 2 short, parallel hallways. The left side hallway had Matt, Clair, and Brian each in individual rooms on the outside of the house. The twins had one large room (originally the master) in the center that opened into both hallways. The guest room was also in the center, on the other side of the connecting hallway that joined the two sides. On the other wall was their parents' room (originally the guest room), Peter's home office, and a sunroom, which was mostly used as storage, but which at this time of year would have been cleared out for guest space.

As Matt cleared the top step he looked up and was confronted with an end on view of Michelle sticking her tongue as far as she could into Mary's cunt as Mary talked nonchalantly, but breathily, about her day while thrusting her fingers into her sisters cunt. Matt just about fell over as he witnessed his sisters 69ing each other on Mary's bed, not caring that the door was open, carrying on a conversation in between alternately licking and fingering each other. Mary, on the bottom, clearly did something right on her end, because Michelle moaned loudly as Matt hurried past, interrupting her thought. Matt rushed into his room, trying to ignore the wet schlicking sounds he was hearing, and closed the door.

"What the Fuck is going on?" Matt muttered under his breath. "Has everyone gone insane? I mean this is... just like..."