Double Dog....

Next, you find yourself kneeling in front of Karen's presented ass, squeezing her cheeks and spreading them to admire her pink asshole and snatch. Her pubic hair is nonexistent around the taint and pussy, confined to a triangular patch north of her clit. Facing the other way, with her head level with her sister's back end, Jenna's eyes are glazed with pleasure as she watches you rub your cock head against Karen's entryway. Jack is doing the same as you on the other side, right in front of his own wife's face. You reach up to stroke Jenna's cheek, and she suckles on tour thumb, moaning.
"Fuck her good, baby..." she says in a half-whisper. "I want to see it... don't hold back... you know he's not goi....nnnngggg!!!!" she cuts off as Jack begins thrusting, and she bites down on your thumb hard enough to make you wince. "Fuck...ah...ah..ah.ah..ah..!"
You match Jack's enthusiasm by fucking Karen in the same rhythm. Soon enough, each sister is babbling and moaning and talking dirty. Karen's snatch leaks slippery fluids all over your shaft and down your sack, until it's enough to drip onto the bed. Jenna collapses onto her arms as Jack pounds faster and deeper.
"Mmm...." Karen fucks back against your thrusts, but she's talking to Jack. "You like my little sister's pussy, don't you? Can't get enough, huh?"
You reach up to grab a handful of your sister-in-law's hair, doubling your efforts in her snatch.
"Focus on your own fucking, Karen..." her eyes roll back to look into yours, and she smiles.
"You see that...ah...ah...Jack....? You see how a real man talks to your wife while he fucks her?"
Jack seems to be ignoring his wife, concentrating on splitting yours in half. For her part, Jenna is moaning wordlessly into the bedspread. It's a little... humiliating to see Jack reduce Jenna to this state so easily. What a little slut she is....
You pound harder, and with more skillful thrusts, keeping your own pleasure razor sharp as you push Karen closer and closer to a g-spot orgasm. Jack seems to sense this, and starts to concentrate harder on fucking Jenna, whose moans are starting to climb in pitch and intensity.