My sister in law Sarah had just broken up with her boyfriend, they were living together at the time so she stayed the night at our house in the spare room.
Her and my wife Lauren are very close and talk about everything. After hours of them talking in Sarah's room, we were all getting ready for bed.
I wanted to check and make sure she didn't need an extra blanket (I like it cold at night) so I knocked on the door, to which she replied "come in".
When I went in the room I couldn't believe my eyes, she was in her bra and panties.
"Oh I thought you were my sister" she said nonchalantly.
I probably should have looked away but I couldn't help but stare helplessly at her fit petite body, and little bubble butt I'm sure she works hard on. She noticed me staring and smiled, giggling a little.
"Can I help you?" She asked.
" Oh I was just going to ask if you needed another blanket". I said.
"Nope I think I'm good, thank you" she smiled and winked.
Turning to head out I gave her one more look, because why not? She made sure to give me a sexy pose before I blushed and shut her door. I walked by the thermostat and set it a couple degrees lower than I normally do and headed to bed.
My wife, (5"5 135lbs, nice ass and DD breasts for visual) was already in bed. She just got off a 13 hour shift at the hospital and was very tired. She was off the next day so she took a generic sleeping pill to make sure she got good rest.
She passed out in about 15 min, I got into my boxers and stayed up about an hour playing on my phone before putting it down and trying to hit the sack.
I couldn't quiet my mind though, I had such a sexy woman next to me, and a sexy one not 20ft down the hall! Minuets passed when I heard our bedroom door crack open. I looked up and could just make out my Sarah'sย outline.
She crept over to my side of the bed and tapped me. I whispered "hey what's up?"
She replied, "it's freezing in my room, I changed my mind on that extra blanket. Can I have one?" I said sure.
I began to get up when she stopped me.
"I need to get warm real quick I'm cold, it's your job to warm me up." Sarah whispered.
I scooted over a little as she gently got into bed and pressed up against me. To my surprise she was still only in her bra and panties!
Feeling awkward that I was only in my boxers I nervously said "you probably would be as cold if you had cloths on."
She giggled and said "Yeah but I can't stand sleeping in cloths. You're lucky I even have underwear on."
Feeling brave I offered "well mi casa su casa. You can make yourself at home."
I kind of added a little laugh to make it seem like I was making a joke. "Ok" She said in a sly call your bluff kind of way, and before I knew it she was totally nude with her underwear thrown on the floor. I could feel myself getting hard, there was no stopping it.
"Feel free to get comfy too" she added.
Without skipping a beat I took my boxers and threw them over her onto the floor. I knew my wife was going to sleep really hard but the thought of being naked with another chick in the same bed as my wife was almost more than I could take.
Sarah faced away from me and pressed her perfect ass into my crotch, grabbing my right arm to wrap around her. There was no way she didn't notice my boner now, poking in between her thighs.
"Sorry" I said kind of embarrassed, but at the same time wanting her to know how well endowed I was (9 inches in length with a very thick girth).
She giggled, "I'd be worried about you if I didn't get some sort of reaction and by the feel of it, you have nothing to be embarrassed about".
She parted her thighs a little and let my hard cock slide up her thigh and smack into her already damp pussy. She gave out a little yelp when it smacked into her clit.
"Oh my God, I had no idea my sister was to lucky!" She gasped
She reached down and rubbed the tip sticking out in front of her. She began to rub her thighs up and down my shaft, once in a while reaching through her legs to grab my balls with her other hand.
I began moving my hips back and fourth. She started taking her juices flowing between her legs and using it to lube my throbbing cock.
"Sarah, are you ok with your sister being in the same bed as us?" I whispered.
Barley getting the sentence out. She just arched her back and pushed her ass into my crotch. I started to fondle her Perky B cup breast and began kissing her neck as I rocked back and fourth.