Well, Dana's right there

You leave the apron behind and walk around the couch to the side where your little sister's resting her head against the arm and texting away. You snatch the phone from her hands; she's chatting with some guy named David, and she's using an awful lot of emojis.

"What the fuck!" she arcs her neck over the arm of the couch to look up at you, only to see your cock looming over her. Dana stares up at it in shock, awe, and disgust; "Why is your dick out???"

"I was about to **** your throat," you explain, and Dana relaxes a little before you continue, "but who's David?"

"None of your business," she snaps reflexively. "J-just give it back!"

"Nah..." You pull up Dana's camera and take a picture of her face with the shadow of your dick across it. "Think of this as an opportunity to showcase your skills. If you prove you can handle my cock **** your pretty face, his imagination will run wild wondering what you can do if you're into it!"

"Y-you're gonna put that in my mouth?" Dana actually looks and sounds a little scared. "I've never really done that bef-FFMMH!"

"Oh, it's going deeper than that," you laugh, thrusting between her lips mid-sentence. You give her a second to get her tongue out of the way, then push past her uvula and watch her throat bulge as you **** yourself into it. You watch your own dick as you pump it in and out, a little mesmerized, until an idea comes to you.

You clutch the upper part Dana's throat and squeeze; sure enough, you can feel your hand around your cock. The thrill of jerking yourself off while fucking your sister's face drives you a little wild. You start pushing deeper and staying in longer, and eventually bottom out with your hips pressed against her jaw. Her throat convulses as her gag reflex fights to clear the passage, and Dana starts slapping your chest feebly.

You realize that your balls are resting against her nostrils, cutting off her air supply completely.