This happened only a year ago and I still cannot believe it happened. We were both 17.
I was spending the night at my best friend's house. Nathan(not his real name) and I had been friends for almost eight years then, but we had never engaged in any sexual activity with each other although we had many very regular talks about porn, girls and masturbation. So we had been fooling around at his place for several hours now while his father was out (his parents were divorced). We played shirtless football and went into the pool for a while and I was already quite horny.
It was around 9 o'clock when, while watching TV, Nathan suggested we should watch some porn on his TV (he was lucky enough to have one in his room)I said 'sure, cool!' so we started with some girl on girl action with dildos and all that good stuff when I heard a banging sound. Nathan had taken off his trainers and layed on his bed in socks. He was now shirtless and showing off his beautiful 17 years old, football player ripped stomach and hairy armpits while he rubbed his dick through his shorts. I got really excited and hard as he slid his shorts off and exposed his seven inch boner poking through the fabric of his black boxer briefs. He made some commentary about the movie which made me feel much more comfortable and I took off my shoes, my shirt and my jeans and also showed my seven inch boner poking though my boxer briefs. 'You seem to be really liking it, huh? If you don't mind I'm going to jerk off now!' I laughed and said 'not at all man, I'm going to beat one off too'. He had now pulled his cock out and was stroking it fiercely. His moans became louder and deeper and so did his breathing. By that moment I had already stopped watching the movie and was looking straight at my friend's huge and hairy cock and was also beating off like mad. Suddenly Nathan's moaning stopped for a second or two as he screamed 'I'm going to cum, man, FUCK' and he started jizzing rope after rope of cum out of his dick head and I came almost immediately as I gave a loud final moan of pleasure. Nathan's bed was covered by both our cums. There were about three seconds during which we were both ejaculating our shit out and during those three or four seconds his father walked in on us and just stood by the door smiling with his hands holding his enormous biceps and said 'I see you've been having fun boys. Please, DO clean up when your done' he laughed and shut the door closed as he left.
I was so embarrassed but my friend told me that, in living alone with his father, it was normal for him to just jerk off with his door open or just walk around the house naked as they had no problem with seeing each other's junk just like that. 'We are both men, there is nothing he has that I don't...it's all just a little bit bigger' Nathan said as we cleaned up his cum covered bed. I was jealous of his father-son relationship.
We have never jacked off in front of each other since that night but we still talk about it and laugh about it. Nathan will be my best friend for many, many years to come and I hope we'll repeat that experience many times.