Carla...

"So, did you hide out the entire vacation? Think I wouldn't notice?" I snarled in mock anger. I squeezed her nipple tightly through the fabric of her shirt and bra, harder than I normally would, but the extra cushion brought the expected inhalation and smile to Kaila's lips...

"Brent, when did you... uhm... figure it out...?" Kaila gasped, playing along.

"I didn't. You two are good, really good." I gripped her free arm with my free hand, and Kaila's smile widened wickedly as she realized what I had in mind.

"You want to do that here?" Kaila gasped again, her eyes darting around the small riverbank. "Nail me right here on the bank of a river..."

"Take you right here, Carla..." I grinned at her. "How many times have you had me inside you already?"

"I promised I'd... never tell." Kaila smiled back, reaching her hand up to grip in my hair. "You really gonna do this, Brent? You really going to **** your wife's sister? You know Dibs just means... first."

"I can't **** you if you're willing." I breathed out, my lips mere inches from hers again. This was amazing how much fun it was. Kaila was really getting into it, and I had to laugh the way her fingers stroked up and down the back of my neck, pressing gently in a soft pattern, like she was playing an instrument.

"Oh, so willing... " She snarled, crushing her lips against mine passionately. Her tongue thrust into my mouth and I eagerly sucked on it, enjoying how aggressively she was returning my ardor.

"Mmm, you're really good at pretending." I yanked, her polo shirt upwards, and my hand slid underneath, gripping her bra tightly. Her nipple poked into my palm as I did so, and I was thrilled to see how excited this game was making her. We had agreed never to break this rule, and now... It was incredible for both of us. There was no harm in it, after all. We were both enjoying the game, and Kaila's response made it all the more worth it. The thought went through my head that Imogene might be getting laid at this very moment.