"Whatever you do for me," I said, "I won't do to Jenna." I swirled my tongue around her back door, rimming her butthole until she was soaking wet with my spit.

"Oh," Mom whispered. "Oh, god, Mark."

"Reach back, Mom," I said, "and pull your ass open for me."

Mom had been looking forward again, but as her hands came back and her fingers cupped the bottoms of her cheeks, she looked over her shoulder one more time. Mom pulled her ass cheeks open for me. As her buns parted, the lips of her pussy spread as well, and I sighed.

Her inner lips were like rose petals in the...