I am sure would have been different if she were fifteen and I was only twelve, but just the opposite was the case. I was almost three years older than my pretty little sister.

I had just “enjoyed” a serious growth spurt and had reached almost six-one and about 165 pounds which was Ok but the big thing, no joke intended, was that my genitals had matured wonderfully and impressively. At least they were impressive to the guys I showered with at school.

It was hard to measure because it curved upward when it was stiff, but it was at least seven and probably closer to eight inches long and about as big around as one of those energy-drink cans, maybe the handle of my tennis racket was just about as thick and hard. I could get my hand around it but she could not.

The head was incredible now when it was excited, purple-red, seriously sloped and bullet shaped with a hard ridge that flanged out and really hooked on when it was fully in. Screams were normal when I fucked a girl, dozens of them, every time I pulled back. I arched them up and tore them deeply.

My testicles had also matured and my scotum was now nearly baseball-sized when it got excited and hard as a billiard ball.

My sister, on the other hand, had been a relatively early maturer and was developing breasts when she was ten or so and a girlish shape by the time she reached twelve. Now she was almost as tall as I am, wonderfully long-legged and well beyond cute. Boys drooled and full-grown men stopped and stared. And she wore the shortest skirts ever seen anywhere.

The fun started when she began having weekend sleepovers the summer after her 12th birthday, and the house was filled with squealing girls in frilly pj’s or tiny nighties. I was in an almost constant state of sexual arousal as they ran around jiggling and displaying their multitude of under-aged charms.

One Sunday afternoon after the three guests had finally departed with more squeals, and my stupid cock had relaxed a bit, she came into my room and stood beside me, wearing nothing but a school t-shirt which barely reached her cute round butt.

“What’s going on?” she asked. “You’re always hiding out when my friends are here, closing your door or going down to the basement.”

I stopped reading the porn story I was enjoying, the one about big brother horsing young sister, put my Mac to sleep and turned to face her, lust in my heart, my balls in turmoil, well beyond tumescent, painfully eager as I had been for a couple of days.

I put my hands on her bare butt and pulled her close so that her pointed jugs were right on my chest and her lips were there to kiss. We kissed.

“Let me show you,” I said when our mouths pulled apart, and we both got our breath. I opened my fly and flopped out my excited but not fully erect member. It just hung there, long and thick and pink, jumping around, the big head swinging from side to side, half way to my knees.

She squealed but I wouldn’t let her go as it rose between us until it was right below her high jugs, now thick and angry looking, the head turning purple. I bounced it off her soft belly.

“See this thing, this big thing.” I pushed it up between her breasts. “When you and your nubile friends go running around almost naked, it gets kind of excited, painfully in fact, and I have to release the tension or I’ll go crazy. So I got downstairs and jerk off at the set tubs. Understand?”