Service her

"Pop quiz, sis: what's the biggest part of me?" she says, grinning.

"Your dick?" You turn your head, wondering why she's asking such a stupid question.

"Exactly. I've always enjoyed how much you love sucking it, too," she says.

"Well obviously, it's the best in the world, and it makes me feel really really good when I put it in my mouth. Is that why you woke me up, you feeling a bit stiff, sis?" You say, giggling at the thought.

"In fact, it is. Thank you for being so understanding, I hope it isn't a bother."

You giggle at such a stupid statement and move onto the floor, pushing her onto your bed as you pull her sweat pants down. Your mouth starts to water as you catch sight of your sister's massive cock in the dim light. Already rock hard, tip glinting with pre-cum, it looks like she had been playing without you.

You start to lick the pre-cum off the head of her cock, savoring the amazing taste before you open your mouth and engulf it. You feel your sis strain as you gently start to bob your head up and down, groaning with pleasure. You look up and her and see her breathlessly staring down at you as you take more and more of her cock into your mouth.

You stop for a moment with your lips around the tip of her dick looking into her eyes. As she opens her mouth to say something you take her cock fully into you, suppressing your gag reflex as you push it all the way down your throat without trouble. Whatever your sister was going to say is lost in a massive groan as she grips the sheets.

Faster and faster you bob your head, before you feel your sister shift. After a moment, you feel her strong hands on the back of your head. Gently, at first, she starts pushing you into a rhythm. You love it when she takes control, and soon she is thrusting into your mouth while holding your head down. You begin to lose yourself in a haze of pleasure, and the rhythm of the act.

Even though you feel like your body is on fire you hear your sister say something as her dick throbs faster and faster. Without a moment's notice, you hear your sister scream in ecstasy as she begins to pump cum into your mouth. Your feel yourself orgasm as your mouth is filled with sweet hot cum, lighting your taste buds on fire with pleasure. You feel your sister let go as you drop to the floor, still swallowing her cum. You lay there, still riding high on the wave of pleasure.