Obediently.

Craning her head back to look up at you with her big eyes, you can see Melanie wavering between hostility and fear. Eventually, either because your magic powers or just in an attempt to avoid Rachel's fate, Mel resigns herself to cooperation. She leans in close to Rachel's sloppy face, scrunches her nose and gives Rachel a peck on the cheek. Then she jerks away and looks back up at you, stupidly thinking that will be enough.

"No, no, no," you say, "you can do better than that. On the lips. With tongue." Mel scrunches her nose even further, but obeys. You and Tommy both lean in to closely watch as Mel forces herself back towards a kiss with her sister's upside-down face. She gags audibly as her full, pouty lips meet Rachel's delicate lips. **** to get this over with, Mel makes an exaggerated smooching sound as the sister's lips press into each other, then visibly sticks her tongue out and plunges it into Rachel's mouth. She can only manage this for a second, though, before she pulls back again, her big tits heaving as she gags from the mix of spit and sweat and cum she was just licking.

"Haha, that was hot," you say as you once again stand behind Mel's heaving body. Pulling down your pants, you place a hand on the top of her head and push it back until she's leaning all the way backwards to hang her head upside down between your legs. "Now put this in your mouth." Mel initially purses her lips and moans, but when you press your cockhead into her face she reluctantly opens up. It can't be comfortable for Mel, still on her knees, to bend her whole body back like this. But you don't care. And as you feel your cock hardening in her mouth, you're getting excited about pushing it all the way in and watching it press against the inside of her stretch-out neck. As you continue to grow in her mouth, you reach down and grip one of her tits - more than a handful - and pull it out of her top. You feel Mel's jaw tighten as you pinch and twist her large areola, but it stays open. You reach in to yank the other tit out by the nipple, more roughly this time, and when it plops out you give it a good smack to watch it jiggle. Again, Mel's face tightens, but in this position, and in this universe, she's unable to dislodge the now erect penis in her mouth.

Meanwhile, Tommy has been playing with Rachel's body while he strokes himself and waits for his turn. Still limply splayed on the bed, Rachel occasionally reaches up to try and push him off, but he easily knocks her arms away. After groping up and down her body for a while, he eventually starts gripping her mouth with his hand to **** it open, then spitting in it and covering her mouth so she's **** to swallow. A tremor runs through her body each time, causing the soft but perky nipples that jut up from her chest to quiver deliciously.

Watching this, it doesn't take long for you to become fully erect in Mel's wet mouth. So far you've been moving yourself in and out slowly, but that's about to change. Gripping a mass of titflesh tightly in each hand, you begin to push yourself in deeper. The head of your cock meets resistance at the back of her mouth, which feels good, but you want to go further. You release her right breast, leaving a red handprint where you were gripping it, and put that hand on the back of Mel's head. Pulling out and ramming yourself back in as hard as you can, you almost cum when your cockhead slams into the opening of her throat, but you still can't make it all the way past. Adjusting for maximum leverage, you use your other hand to grip Mel's throat right under the chin. This time, when you slam your shaft hard into the wet hole, it goes all the way down.

Sure enough, you can clearly see the bulge in Mel's throat where your cock has penetrated. As you ram it in deeper and deeper, you viciously jerk Mel's head back and forth around your cock. As her body jerks from your efforts and quivers from her own gag reflex, Melanie's giant boobs jolt around violently, often slamming into each other with a satisfying thump. As you keep increasing the pace at which you're jackhammering into her open mouth, you reach one hand back down to pinch a nipple and help her tits slap into each other even harder. Your balls tighten as they continue to pound into Melanie's nose, and as you feel yourself about to cum you make the big tit whore tighten up by bringing your palm down hard next to her nipple, right in the area that was already red from before. Her entire body convulses, creating an epicenter of friction around your cock. With immense satisfaction, you empty a massive load of semen deep inside Melanie's throat. Whew. That was fantastic.

You squeeze your thumb and index finger around your shaft so you can empty every last drop of cum you have into your sister's throat while you pull out. Her eyes, which you haven't been able to see since the facefucking started, are leaking mascara down her forehead and into her hair. Her arms are quivering, and as soon as you're no longer holding her up she collapses backwards onto the floor. Still fully clothed except for her top being pulled under her breasts, Melanie already looks just as devastated as Rachel. She mumbles something about being able to go now that she did a good job, but you ignore her.

"Now you're going to do that for Tommy, right Mel?" She turns her eyes, which are red from the sting of mascara and spit and cum, towards you, and gives an obedient nod. Tommy grins.