Define 'Incest'

For the next few days Gwen and Ben took every chance they had to cum with each other, but never getting to ‘intercourse’. They came at least three times a day each when their grandpa was around, and when he wasn’t it nearly tripled. One day though, after a particularly intense session of oral sex, they looked into each other’s eyes. They stared at each other, both with an intense lust in their eyes. Their grandpa was gone for the day, he was fishing for salmon in a stream a mile away. They were as alone as they could be. They stared deeply into each other’s eyes, and nodded. They left the shower, the scene of most of their ‘activities’ and walked to their beds. They laid down on the bottom bunk next to each other.
Ben looked at Gwen, and Gwen looked at Ben. He got up on his knees and positioned his rock hard 7 inches in front her dripping cunt. They gazed lustfully into each other’s eyes. Days of ‘outer course’ and taunting and tease and wrestling were about to cum to a head. He licked his lips, propped himself up with his arms above Gwen. She quickly lurched forward and gave him a kiss.
“Are you ready?” he asked, half horny, half nervous, and half lustful.
“Oh god yes.” She whispered. He slowly inserted himself into her warmth. She gasped loudly as he slid in, and gave a short whimper of pain when he passed through her virgin membrane. The pain was intense, but slowly was replaced by a stronger pleasure. Ben was completely inserted in Gwen. He was in shock at the pleasure. His head was swimming. It was better than any blowjob Gwen had ever given him since they started. He was sweating and gasping already, trying not to blow his load this early. He hadn’t even began thrusting yet!
Gwen, tears in her eyes from the pain, was beginning to feel the pleasure in this. His cock was touching her in places that his toungue and fingers never reached before. The pain was completely gone and her now impure pussy was clenching around the giant intruder. They lay there, Ben, arms locked holding him above Gwen, pressed so hard and deep into her that their stomachs were even touching, Gwen, staring wide eyed up into Ben’s eyes. The pleasure was so intense that both of them were less than an inch from the greatest orgasms of their lives!
Ben wasn’t sure what to do yet. His hips wanted to thrust but his dick was afraid that if it moved the pleasure would be gone and never return. Slowly, he began to retract from Gwen, causing another wave of intense pleasure. He began to pump in and out of her, slowly at first, but quickly picking up speed. They both started moaning, but never breaking eye contact. The bed began rocking, and the blankets and pillows were sliding out from under them and onto the floor. Gwen rapped her arms around his neck and her legs around his hips and ass as she began to scream with pleasure. Ben began thrusting so hard that the entire RV began shaking. At one point Ben pulled out to fast and too far. When he tried to get back into Gwen he missed and went a little lower, into her ass. He thrust in so fast that Gwen’s moans of ecstasy stopped and she gasped. So did Ben.
The difference if feeling was amazing. Ben, who was on a roll now, instantly began thrusting in and out of Gwen’s tight ass. It felt much different from her pussy, but every bit as good. It also allowed Ben to slip his hand between them and finger her clit. Gwen, who was already on the verge, was just about to go over. She looked into Ben’s eyes and kissed him as she climaxed.
The feeling of Gwen’s toungue in his mouth and her pussy juices flowing over his hand sent Ben into an orgasm as well. They moaned into each other’s mouths as their orgasms subsided. Then they laid back down, Ben still in Gwen, on the bed. Ben pulled the pillow under Gwen’s head as he laid on top of her and pulled the covers back up over them and they fell asleep. The summer had gotten a whole lot better. The end. (there will be no more chapters.)