This happened when I was 15, TRUE, and I remember it like it happened yesterday.
When I was 15, my best friend and I used to jack off together all the time. We usually sat on the side of his bed with a magazine showing a woman's tits, laying on the floor so we could see it. We did this a lot after school. We always locked his door.
One afternoon after school we talked about hot girls at school and what they probably looked like naked as we walked home. We were both hard by the time we got to his house. We went upstairs into his room and got his magazine out, but we forgot to lock the door. We were both sitting on the side of the bed with our pants around our ankles jacking off when suddenly the door opened and his 14 year old sister walked into the room! Whoa!
She immediately saw what was happening and she said 'I'm gonna go tell Mom!' We immdeiately started begging with her to not do that. This went on for 5 minutes as our dicks shrank and were were hurridly pulling our pants up. She finally said she wouldn't go tell their Mom, but she wanted to watch us finish. Those were the conditions. She kept insisting and we had no choice. My friend locked his door and his sister kind of kneeled on the floor in front of us. We gradually got hard again. I know my friend was embarrassed and humiliated, but I rather enjoyed his sister seeing me.
She looked down at the open magazine and asked us if the woman in the magazine excited us. We told her it did. As we stroked and she watched she finally said 'You wanna see my boobs?' 'Hell yeah!' I said. She changed to a cross leg sitting position and took her top off along with her bra. For a 14 year old she was looking pretty hot! She leaned back resting her palms on the floor behind her and she looked down at her boobs saying things like 'they're getting bigger ... do you like my nipples?' It was sexy as Hell. She started talking about our dicks and she took his and mine, one in each hand and felt them, and talked about how hard they were. Then she asked if she could jack us both off. 'Sure!' we said in unison! Kneeling between us, one dick in each hand, she started jacking us off. Not only did it feel wonderful, it looked so hot seeing her do this to us topless. It wasn't minutes and we said we were cumming and she aimed our dicks at her tits and we started shooting cum all over them. Seeing my friend shoot cum on his sister's boobs, while my dick was right there near his shooting cum was one of the hottest things I've ever seen or done. Today, 20 years later I still jack off thinking about that day.
She wiped all the cum off her chest with tissues and this time she made US promise not to tell. Of course we weren't!! We never did this again as a threesome. HOWEVER, one day I went over to his house and my friend was gone all day to a scout outing, so it was just his sister and me.
Within an hour of some suggestive talk, she asked me if she could jack me off again, so she again took her top off and jacked me off on her boobs. This time without her brother there, she also let me feel her tits and she showed me her pussy too. I will never, ever forget these two incidents. Not ever!