Sam explains and continues

Sam popped my cock out of her mouth and whispered, "That little display upstairs got me so horny, Dan. I've been waiting for a chance." She took my length back in her mouth and resumed sucking and licking it.

"But what about your sister?" I quietly replied, not wanting to use her name in case she awoke from hearing it. I was freaking out, but kept my voice calm.

"Didn't she ever tell you we shared guys a couple times when we were in high school, before she met you?" she asked with a sexy smirk. "I'm sure she'll be okay with it."

My eyes went wide as she'd never told me. My cock lurched, poking her in the face.

"Oh, you like that idea, huh?" she said with a grin. Then she took the head and stuffed it down her throat.

"Ah!" I exclaimed because Sam began playing with my balls. Meghan stirred slightly, but settled back to sleep.

My sister-in-law's oral skills were as good as Meg's, but the risk of the situation made everything better. I guided her head up and down, and reached lower to fondle her breasts. She starting licking up and down the shaft while gazing heatedly up at me. She smiled around my thickness. She began attacking it with more vigor, her tongue swirling wildly around it, and I had trouble keeping quiet. Then she moved her hands to a breast and her clit, making her moans get louder, though muffled by my cock. She must have been really close, because she took me to the root and started swallowing, which squeezed the head in the back of her throat. I stifled a scream as she moaned into my meat, and my cock spouted in her mouth. She kept bouncing her head up and down as we both came, swallowing every drop.

After recovering for only a few seconds, Sam rose up and leaned over, kissing me and thrusting her tongue in my mouth, along with a bit of my cream. I chased her tongue until she broke the liplock.

Then she covered me up and blew me a kiss as she headed up the stairs.