My Stepmother whom i also call 'Mom', and I had been alone since Dad passed away five years ago. It had been hard losing a father at the formative age of ten. Despite that, Mom's loving attention had steered me through the rough years of puberty, into a short-lived teen rebellion, and to where I was now; a relatively healthy, mentally balanced fifteen-year-old. Being fatherless had forced me to grow up faster than some of my friends.

Mom gave me my dark complexion from her South American heritage. She had impossibly dark, thick, glossy hair flowing to the middle of her back. She was petite, and I mean really petite, standing less than four feet, eleven and a half in bare feet. I'm surprised I didn't inherit that trait from her. Actually, I'm forever thankful my height came from Dad who, at a sigh over six feet, used to tower over Mom. Mom, at thirty-seven, had retained her shape after giving birth thanks to a dedication to yoga. She wasn't body-conscious; it was fitness that drove her, a requirement for an active sports social life. With the exception of a slight rounding of her lower belly you'd never guess she had a fifteen-year-old son.

I wasn't ignorant of the benefits of an active physical regime, either. Being in the middle of raging teenage hormones, I had no problem admiring her slim physique. She was, perhaps because I was around her so much, my definition of what a sensual mature female should be; her hips still slender flaring to curve around a beautiful pear shaped rear, shapely legs, and tiny ankles and feet. With her beautiful smile that seemed to light up a room and very unusual sparkling blue, expressive eyes that could dance with mischief glee or punish worse than harsh language, it was hard not to stare at her. In fact many men did, much to my consternation. I mean, it was my Mom for goodness sake.

Our life was fairly comfortable. A reasonable life insurance policy on Dad meant Mom didn't have to work. While I busied myself with all the normal activities of a young man, video games, sports and lusting after anything in a skirt or with boobs, Mom kept herself occupied with home, charity work, tennis, golf, and an extensive network of friends.

My relationship with Mom was unusual; it was really good. We talked a lot when I was home. With the exception of very personal stuff there was no subject we couldn't carry an interesting and easy flowing discussion on.

On this night, everything was the same as usual. Mid-May meant the weather was coolish in the evening. The usual routine for a Friday night was for me to head out with some friends, perhaps to hang out with some girls at the mall or visit the local arcade or, even rarer, take a date to the movies - I was somewhat shy and hesitant around girls. Mom usually had some social engagement with one or another of her friends.

So when I say everything was the same as usual, I meant except for a couple of things. My rare and thus much anticipated date had cancelled due to some family thing that popped up, so I decided to stay home and watch TV. At around nine I finished a beer - Mom let me have some on the theory that it was better to learn to drink at home than get wasted when out - and went up to change into my pajama bottoms and a tee. I was way too cool to wear a pajama top. I figured I'd have another beer and snooze in front of the television until Mom got back; a perfect use of energy balanced with an ideal amount of brain activity for a Friday.

About nine-thirty I heard the front door open and Mom enter. It was a little earlier than she usually came home.

"Hey, Mom. What's up? How come you're home so early?"

"Nothing special, David. I wasn't really interested in going out on the town for a drink with the girls. What are you up to?" she asked, walking into the den.

"Watching a movie and having a beer."

"What movie?" she asked.

"Two Weeks Notice with Sandra Bullock and Hugh Grant. It just started." I know, a fifteen-year-old guy watching a romantic comedy? So sue me. I love romance when there are great comedic moments building the storyline.

"Maybe I'll join you," Mom said, smiling that wonderful smile.

"Sure. Good idea."

With Mom heading out of the den, I went back to watching the movie. It must have been ten or fifteen minutes later when I heard her come downstairs, the fourth stair from the bottom creaking. Some rattling in the kitchen followed and then she appeared in the den.

A quick look at her and I saw she'd prepared for bed too with one of her well worn soft long tee shirts and a glass of white wine in her hand. Now, we have a couple of armchairs in the den, comfortable enough in their own right, but only the one couch. And quite honestly, I was glad I had dibs on it. It was the most comfortable spot to watch TV. I expected her to take one of the armchairs but she surprised me. She came over to the couch and, putting her glass on the coffee table, started to sit. I quickly twisted onto my left side, against the back, giving her room to sit.

"Do you mind if I share the couch?" she asked.

"No problem." Feeling only slightly put out at losing my comfortable position, I started to sit up.

Mom put her hand on my shoulder saying, "No. Don't move. I'll lie down beside you."

With that she rolled down in front of me so we ended up in a spooned position, about three inches apart. This wasn't the usual position for us to watch TV, but being so petite I could see over Mom's head and easily watch TV.

"Can you see?" she asked.

"Yup."

Mom and I had a great relationship, we were more than the average mother and son. We talked and enjoyed each other's company a lot, unlike my friends and their mothers. However, we were not an overly physical family. Sure I'd reluctantly give her a hug if it seemed she needed it. She'd give me a quick kiss on the cheek if there was ever a reason. But that was about it. So when she plonked herself down in front of me, it was a first. And truth be known, it sort of felt nice, cozy. Looking down at her hair I appreciated how thick and shiny it was. Even the scent of her shampoo was nice.

We watched the movie for a few minutes. Then she reached for her glass of wine. As she reached, her back arched and her bottom pushed back. While up to this point there had been nothing sexual about our situation, I was fifteen. The feeling of firm buttocks pressing back into my crotch was VERY interesting, no matter whom they belonged to. After her sip of wine she again reached out to put the glass back and her buttocks once again pressed into me.

Now I don't know about you, but at fifteen, the vibration from a lawn mower or even the pressure of a counter edge can give me an erection. In fact, pretty much anything can do it. So when Mom pushed her rear back into me the results were no surprise; my penis twitched in response and started to wake up. No, I wasn't responding to my mother in a sexual way. My body was just responding to the pressure of a female rear end. None the less, I was embarrassed.

After Mom finished putting her glass down, she once again settled her head down and watched the movie. I breathed a sigh of relief. How exactly would I explain an erection, well really a partial erection, to Mom?

Five minutes later Mom must have decided to get more comfortable. She reached for my arm and pulled it under her neck to her front where she held it. With her lying on her left, my hand rested under her neck and up across her body, my hand just above her right hip. I was happy. My arm had slowly turned numb in its previous position up against the arm of the couch. It now tingled back to life.

Then with a sigh, Mom made a wiggling movement which scooted her body back into me; full contact from shoulder to ankle, knees bent.

Now I can say that under other circumstances with any other female I would have relished this cuddling. I'm an ass man. I love beautiful pear-shaped asses, and the crease where the cheeks meet the thighs on a girl is the sexiest sight I can imagine. The thing is, this was my Mom! But what did hormones care? The feeling of a soft and firm bottom pressed back against my groin elicited an immediate reaction. I felt my penis begin to expand despite my abject horror at the situation. I pushed my butt back hard into the couch to try to limit contact.

Unfortunately, two things happened with this move. My penis decided this was perfect for it to spring up, now there was no restraining pressure, and align itself towards my navel. The second disastrous event was Mom wiggling her bottom backwards to re-establish contact. And she did. Now I was mortified as my penis happily found the groove between her buttocks.

Mom's movements stopped. I'm pretty sure she realized her son had an erection. Hell, it would be impossible not to notice at that point. I wrestled with what to do. Should I get up and go to my room? Should I lay there and ignore the situation and hope my erection would fade? This was a severe dilemma for me. I wasn't harbouring any secret desires for Mom. I hadn't wanted my body to react this way. And to top it off I was really embarrassed.

Deciding retreat was my only option, I made to move off the couch. "Mom, I think I'll go to bed now", I said softly.

Mom reacted by holding my arm tighter. "Not yet David. Please, let's just relax like this until the end of the movie."

"Uh Mom..."

"Shhh," was her immediate response. With that she cuddled back against me, watching the TV.

It wasn't nearly so simple for me. The feel of her buttocks against my groin was fantastic. My penis was perfectly aligned between her cheeks, so warm, comfortable, firm and soft. I couldn't control the pulsing throb of my traitorous erection and couldn't not think about it. When you're an ass man, this is the type of situation you dream of, just not with your mother.

Nevertheless, I resolved to concentrate on the movie in hope that it would distract me enough for my penis to get a conscience.

Okay, that didn't work out as planned. No matter what was going on in the film, I couldn't get my mind off the wonderful comfortable and sexy position I was in, and my erection remained determinably firm. I was the good son, though. I didn't move an inch, lying like I was dead meat in order to avoid triggering any further reaction that would heap further embarrassment on me.

That worked until...

I felt Mom's cheeks stroke my erection slowly when she bent for her glass of wine! The pressure on my penis was exquisite, her buttocks gently and slowly squeezing around it generating an automatic sympathetic pulse of my own. I could feel a wet spot developing at its tip. My embarrassment was overwhelmed by teen hormones; it just felt so damn good.

I lay as still as road kill, enjoying the sensation. When the wine glass was returned to the coffee table her buttocks relaxed from holding my erection like a hot dog coddled in a soft bun.

I wondered what was going through Mom's mind. Why had she clenched her buttocks? It wasn't as if she had been celibate all these years; or at least I thought not. Perhaps it was just an accident. I could live with that. Between the clenching of her buttocks and the feeling of her shapely, soft, firm bottom pushed into my groin, I had food for several evenings of self gratification.

Unable to stop myself, I closed my eyes and pictured Mom's perfectly pear-shaped ass in my mind. God it was lovely. Until now, when I had admired her rear it had always been as an inanimate object. Somehow I always enjoyed the sight but never associated it with sexual feelings for Mom. It was like looking at a perfect piece of art; very subjective with no care for the artist. But now, with one arm around her and the feeling of her bottom firmly pressed to my groin, there was absolutely no question I was thinking about sex, and a little of the artist, too. It was very arousing, too arousing.

When she reached for that damn glass again, her butt cheeks massaging me, my response was immediate.

With a grunt my scrotum tightened and my penis expanded and I ejaculated time and again into my pajamas. Mom's bottom was nestled tightly to my erection as spurt after spurt of hot semen exploded out, soaking me.

Finally, after what seemed like hours but was probably less than a minute, my spasms died down.

I immediately felt guilt, shame, and embarrassment wash over me. I wanted to apologize, say how sorry I was that I had cum, and try to rationalize away my inappropriate behavior. I was confused to say the least. But more importantly I wasn't relaxing in the afterglow of an orgasm, one brought on by an incredibly sexy, firm, soft, beautiful bottom. In truth, I was mortified.

What should I do? Say sorry or just get up and leave, which my mind was screaming for me to do. However, before any of these conflicts could resolve themselves in my mind, Mom moved. She rolled forward slightly and sat up. Reaching for her empty glass of wine, she rose and walked towards the kitchen. As she walked away I could see the damp stains of semen on her night shirt at the top of her ass.

Without saying anything or even looking at me, Mom left the den, passed through the kitchen and headed upstairs.

I lay there mortified. It didn't occur to me that Mom might have been an active participant in what happened. All I knew was I had possibly ruined my relationship with her. How could things ever be the same? For that matter, how could I ever look Mom in the eyes without feeling ashamed? Instead of feeling the warmth and satisfaction of a great orgasm, I felt like a prig. With a deep sigh, I got up, turned the TV off and headed up to my room. Cold sticky semen in my pajamas did not feel good.

After cleaning myself in the bathroom, without putting on new pajamas, I fell into bed and tried to sleep.