Let me a start off by saying I'm an average 18 year old male (at the time) with a 5.5' dick, and I have a 15 year old sister who isn't super attractive but I've always had sexual thoughts about her.
I've always wanted to try to have some kind of masturbation session between us but have never been able to initiate anything. After reading some stories on here I've decided to try to smell her panties sometime and thought it'd be a great idea. So one day when our parents were gone for the weekend and she was at a friends house I decided to go for it and went into her room to find her laundry hamper full of clothes as she woke up this morning and left soon after.
Right near the top of the hamper I found her PJ's and a pair of blue panties that were still warm. I was so nervous and already had a boner tenting in my shorts. I slowly lifted up the panties to my nose and took a whiff. The smell was incredible and to me indescribable. The smell made me so horny I could blow my load right there. But just then I heard my sister come in the front door downstairs and I panicked.
I didn't want her to see me in her room smelling her panties with a tent in my shorts but I still really wanted something to happen between us so I figured I'd go to my room across the hall, strip and jerk off in there to wait for her.
I quickly got to my room and left my door ajar just enough that if she came upstairs she'd notice. I was on my bed fully naked and tried to act normal and also tried not to jerk off too much otherwise I'd blow my load soon. I heard her come upstairs and I could see her about to walk past my door and then she stopped and slowly opened it. I quickly covered myself up asking what she was doing (pretending it was a surprise) and she was in awe as she saw her brother almost completely naked.
She slowly walked in and stood in front of my bed and though super nervous I slowly pulled my blanket off my crotch as my sister watched. I let my hard dick spring out and point up. I was already leaking a tiny bit of precum from everything that was happening and my heart was racing. I could see my sister slowly rubbing her crotch over her tight yago pants and she had a tank top on with apparently no bra as I could see her nipples hard. I nervously asked her to join me.
I could see she was clearly hesitant but she seemed so horny also as she slowly took off her tank top exposing small breasts (still developing but a fair size, don't know the size though) and her super hard nipples. She sat down right beside me hinting at me to touch them as she reached down to grab my dick. As she grabbed my dick it felt amazing and I fought not to cum right then. I took a hold of one of her breasts and massaged it and rubbed her nipple. Her face was ecstatic this whole time. I took a hold of the edge of her pants and pulled them off and she was wearing a pair of pink panties and I could see a wet spot right over her vag. This turned me on so much as I've never seen a girl this naked before.
I slowly started rubbing her over her panties and she felt soo wet. I decided to pull her panties off and as I did I saw her tight pussy with a little hair on top that's never been shaven. I started rubbing her and she was so wet, I slowly put a few fingers in and after a while of rubbing and fingering her I could feel her clench up and explode. She said it was her first orgasm as she squirted her juice a few feet away from her and I pulled my hand out soaking wet.
I was so ready to cum at this point so I told her to return the favor. She grabbed my dick again and started stroking it very fast and in just a minute I shot ropes of cum into the air, to my face, all over her hands and everywhere else.
We both just lay there exhausted and still horny. We smiled at each other as we've only spoke a few words during this whole event. We got up and showered together and had even more happen in the shower, but that isn't for here. We have had many more of these events since that day and we are even closer now.