This was the first time I jacked off looking at my sister, but notice I said the first time. Let me know if you would like to hear more via the comments section.
My sister Linda was born about a year before I was. We're the only two kids our folks had, but it was enough. Oh yeah, it was enough.
One hot weekend during my last year of high school, Linda had a friend of hers, Julie, over to stay. Mom and Dad were out of town visiting mom's folks, so we had the run of the house. Julie and Linda were a lot alike. Both of them were about five foot six, sandy blonde hair and built really nice. Linda's tits were a little bigger than Julie's, but Julie had the nicest, hardest ass of any of Linda's friends.
Anyway, on Saturday the two of them were out in the back yard catching some sun. Our yard had one of those eight foot privacy fences around it which made for some interesting times. I was upstairs in the spare room overlooking the back yard, watching through partially opened blinds. After they got their towels all situated they began to oil themselves down.
About this time I pulled my cock out of my shorts and started to slowly stroke it awake. With their arms and legs glistening with oil, they took turns spreading it on each others backs. Linda was lying down on her towel as Julie put oil on her. Julie seemed to take a little extra time putting it on Linda, even running her hand up under the waist of Linda's bikini bottom. Linda just smiled and I could hear her tell Julie how good the oil felt on her skin.
My cock was getting really hard now as I watched with growing interest the action in the yard. I began to stroke my engorged cock faster as Julie untied her top and laid on top of Linda's back, rubbing her firm, hardened nipples all over her. I could feel the cum boiling up in my ballsack as Julie started humping Linda's ass. When Julie reached her hand around and under Linda's bottom I couldn't hold back anymore and thick streams of cum began shooting from my cock!!
I must have groaned out loud because when I opened my eyes, Julie was sitting up covering her tits with her arm and her and Linda were looking all around, trying to find the source of the noise. I slowly left the room and went back to my bedroom where I started thinking about what I had just seen and got hard all over again. After what seemed like an hour I brought myself to another wonderful orgasm, spraying cum up onto my belly and chest. Ah, Julie and Linda, what a wonderful pair.