This was from a prompt from over at r/dirtypenpals, but the user deleted their account. Not wanting this to go to waste, I present it for your smutty indulgences. I can continue it if there is interest.
The background: You are 27, living in the city. I, your little brother, am 22, living with you as I work on my degree. You went out partying tonight, hoping to catch some dick and end your dry spell. I'm asleep when you come home and stumble, drunk, into my bedroom.
"Hey, Sis, you okay there-" I start to ask as you look hungrily at me. You have this primal lust in your eyes that I've never seen before. Sometimes, late at night, when I couldn't sleep, I would briefly think about about you coming in like this, drunk, disheveled and horny.
My words are cut off as you press your lips against mine, as your hips straddle mine, trapping me under my covers. I sleep in just my boxers most nights and I become very aware of this fact as you sit on top of my growing erection, grinding back and forth eagerly.