I drop in here from time to time and am amazed at the amount of stories dealing with siblings. Most of them obviously aren't true but mine is.
The summer before I began 9th grade was one of transition, as me, my mom, and sister Laney had suddenly moved nearly 400 miles from where we grew up. It was very hot and neither me or my sister knew a soul, as school wasn't in session. We didn't do a whole lot except sleep, eat and watch TV and junk.
My sister and I had already had a few sexually involved encounters together - one with a teenaged babysitter named Anne who liked to get naked with us (by playing abbreviated games of strip poker) and encouraged us to suck on her nipples while she had her hand jammed in her panties, masturbating. I can't remember if my sister and I had any sexual contact during these goings-ons, but I do remember having a very hard cock and remembering her mons and how it got puffy-looking when she was sexually excited, happily sucking on our young babysitters hard nipples.
During the process of unpacking from the move, I had found one of those old plug-in back massagers with the coils that slipped over the back of your hand. Well,I quickly learned that putting the massager right below my penis's head on the foreskin felt tremendously good. It makes my cock spring to life just typing this remembering how great it felt on my rock hard penis.
Apparently, the humming noise it made was really loud, and one afternoon my sister barged in my bedroom, catching me red handed masturbating my cock. She spent the rest of the day torturing me, saying she was going to tell our mom, and of course at the time I believed she would. She finally said she would keep it a secret if I let her "see it", meaning my cock.
One thing led to another, and in less than a week my sister and I were getting completely naked in practically every room in the house and masturbated in front of each other every single day.
Obviously, things progressed to mutual masturbation and some dabbling in oral sex. It was the best summer ever