This happened when I was 17 and my sister was 16.
My sister and I were in my bedroom talking one summer day years ago. We were talking about sex. She was asking me if I had 'gotten any' yet. At the time I had been jerked off by a few girls I dated but I was still a virgin. I did tell her I had received a few handjobs but not much more.
I asked my sister if she had 'gotten any' and she said no, although she had recently started dating. She just hadn't gone that far yet.
She looked very intrigued and she asked me about the handjobs. I told her it was a heck of a lot better than getting nothing! She asked me if it felt good and I told her it felt wonderful. I asked her if she had felt up any of the couple of guys she had dated, and she blushed and said no. She said 'what do you do ... just kind of move it up and down?'
I said 'yeah, sort of.' I was kind of getting turned on talking about this stuff with my sister. I could also tell she was enjoying it more than a regular conversation too. Her face was kind of flushed. I said, 'if you want to, you can jack me off so you'll know what you're doing when the time comes.'
She sat there looking at me. I could tell she wanted to but wasn't sure what to say. She asked me if I was getting hard, and I told her I was getting REALLY HARD! At that point, I spread my legs as I was sitting in the chair and the bulge in my pants was very obvious.
'OK .. yeah. I want to see it and teach me how to do it' she said. I stood and slowly took my pants and underwear off. My dick was as big and hard as my 17-year-old dick could get! (Which was pretty large at 17)
'Oh my. you have a BIG dick!' she told me. I stepped over to her as she was sitting on the edge of the bed and I took her hand and placed it on my swollen throbbing dick. Being the first hard dick she had ever seen or felt, I loved her gently feeling me and slipping her fingers around my dick, then checking out my balls. The look on her face was one of thrill and also concentration. She was studying my dick. I laid my hand over hers and began the stroking movement and I told her that's all she really had to do.
I was about halfway to cumming when I told her that I had never fingered a girl yet (which was a lie because I had.) I asked her if I could finger her pussy. She was already so excited jacking me that she readily agreed and she pulled her jeans and underwear off. Mmm. My sister had a yummy mound of dark brown hair and her lips appeared to already be wet. She stopped jacking me while she laid on the bed and spread her legs apart. I slipped a finger in her hot wet pussy and felt her inner walls and juicy insides. I really didn't even know what a clit was then so she located that and showed me and asked me to gently rub it, alternating with fingering her now and then for moisture. I did that for a while, then she sat up and sat on the edge of the bed far enough out that I could stand and lean over and finger her as she resumed jacking me off.
She even told me ...'damn this is fun!' I told her how damn good it felt and I told her I was about to cum and don't stop when I start spurting. I was suddenly shooting ropes of cum onto her t-shirt. Damn. I hadn't even gotten her out of her shirt!
I don't think I came close to actually satisfying her pussy. After I came we more or less stopped and cleaned up.
It wasn't a week later when we were home alone again and I asked her if she would jack me off again. She said 'SURE!' This time she got totally naked and I did too. She let me suck her nipples for a long time. She had small pink nipples on about 34B breasts. They were NICE! She jacked and I fingered much as the time before. This time though she finished herself off with her own hands and I watched. I loved seeing her eyes closed, concentrating on the feeling and her contractions as she came.
The next time we got together, not days after that, she asked me to jack off for her so she could see how I did it.
All in all, my sis and I probably got naked and masturbated about 20 times in a year then it gradually came to a stop. But what FUN! Today, years later, I still jack off as I remember those episodes. My sister is a great looking lady with three kids today and I'm sure we won't ever re-live those days, but oh the memories!