This involves my college friend and his older sister.
My best friend in high school and I were both home from college (we go to different schools) and we were in his basement watching some porn on the big screen tv. It was late on Saturday night and we had the house to ourselves as his parents left that afternoon for the rest of the weekend and his sister was away at school. We had messed around while in high school so were quite comfortable being naked with each other and had stripped off and sat next to each other alternately playing with ourselves and each other while watching this big tit blond masturbating two guys at once.
We were both horny as hell and constantly edging. Then one of the guys on the screen grabbed the blond hair and pulled the head down to his crotch. Then we saw the shaved and cut dick slide into the mouth. "Oh shit I wish that was my dick in a mouth" exclaimed my bud. I responded that I too would like to feel a wet mouth on my dick. "Well, then why don't you just suck each other?" came a voice from behind us. We jumped and turned to see his sister standing behind us, all her clothes were on the floor and she had three fingers up her slit jilling like crazy. "What the hell" shouted my bud.
His sister just walked around and sat between us and started playing with our balls and penis. Her brother wasted no time in fingering her cunt and told me to suck her tits that she really liked that. After about 15-20 minutes she asked when we were going to suck each other because she wanted to watch. We both said no way, we are gay! She responded, "look I know you guys have been masturbating each other since middle school, I used to spy on you and get myself off watching you." I said, "shit, you've been perving on us for like 6 years? That's just weird. We are not gay, just a couple of friends helping each other get off." "Yeah, and my brother and I have been helping each other get off for a while now, so I think it is time we all took this to the next level." "No way, that's just way to gay to suck some guy's dick, if it is best friends. No guy is going down on me and I sure as hell not going down on a dude. Sorry, bud, no disrespect, but that is just way too gay!"
His sister goes, "have either of you ever had a blow job from a girl?" My bud said, "I wish" and I said the same. My bud then says he is so horny he is willing to try anything. His sister then said that she bet neither of us could tell if it was a guy or girl sucking our dicks. I was so hard and had been for so long that it was beginning to really hurt. Her suggestion, that since her brother was willing to give it a go, for me to get blindfolded and let each of them have a go on my dick and see if I could tell difference. Well by then I was so turned on I was willing to give it a try. I was blindfolded and hands tied behind my back and placed in a recliner. I let out a gasp when I felt that wet warm mouth engulf me for the first time. I almost lost it right off, but held off. After just few seconds, my dick flopped out of the mouth and then back in this happened several times. After six times I asked to say which mouth was on me the first time and the last time. I had to admit that I could not tell if it was a guy or girl going down on me. Then I was again engulfed and this time almost brought to organism then nothing. After I begin to come down from the edge I was engulfed again and I was really getting into it when asked if liked the current or first the most. I couldn't really tell any difference but didn't want to stop so I just said I really like it now please keep going. My blindfold was removed and looked down to see my bud on me while he and his sister masturbated each other. You never know where mutual masturbation will go!