This is true, and happened in 1972.
I had felt a dull ache in my left nut while showering, and when I got back to my dorm room, I was inspecting it to see if I could see what was causing it. I had my leg up on my bed, and feeling my nut with my left hand, when my room mate Kyle rolled over, looked at me, and asked me if I was having a good time. I told him my nut hurt, and asked him if he ever had that. Kyle surprised me by saying 'only if I go more than eight hours without relief', because we had never talked about jerking off before, even in kidding. I pinpointed the pain at the point where those tubes enter the nut, and was comparing the ones on the left nut to the ones on the right nut, when he asked me if I found anything. I told him where it hurt, but that it didn't seem swollen or anything, when he said 'show me'.
I walked over to his bed, and pointed to the spot, and he reached up and cupped my nut. I jumped back in surprise, and he told me to not be an idiot, to let him see. I slowly walked back, and he cupped it again, and started to feel the spot with his fingers. Then he pushed his comforter down, slid his other hand into his boxers, and said, 'its definitely more swollen than mine', and took his hand away. I said really? And he stood up dropped his boxers, and said yeah, see for your self. I reached over felt his nut, found the tubes, and they definitely were smaller than mine. I looked down at Kyle, and saw his dick was rising, which caused mine to stir as well.
In seconds we were both sporting raging hard-ons, and still had one hand on each of our nutsacks. Kyle let out a little sigh, and I moved my hand to his shaft. He reached over and wrapped his hand around mine, and we starting jerking each other off slowly. Kyle finally broke the silence, saying lets lay on the bed, and we moved over to his bed and laid down, and starting jerking each other again. It felt so fucking good. Kyle started to leak a lot of pre-cum, which surprised me, because I never did that, and I didn't even know what precum was. I asked him what the deal was, and he explained that he always did that before he came. Kyle whispered that he was close, and let my dick go, and leaned his head back and started to stroke his chest and nipples with his hands. He grunted a couple times, then thrust his hips upwards, and his cum spurted up onto his stomach and chest. This also surprised me, because mine always just dribbled out. He was breathing hard, and pushed my hand away from his dick, and then went back to jerking me off. He wiped some of his cum onto his palm and fisted it into my dick, The slickness took me over and I came as well. We both laid back on the bed, still breathing hard, and then Kyle asked if my nut felt any better.
For some reason I thought that was funny, and started laughing, and he starting laughing too. I looked at him and said 'shit that was the best nut I've ever felt' and then we both starting laughing again. Kyle and I jerked off 100's of times together after that, sometimes each other, sometimes just ourselves. Watching him nut always turned me on, and doing it together was much more intense than doing it alone.
Turns out I had a varicose in my left nut, which healed itself.
We are both married with grown kids now, but still get together a couple of times a year and jerk each other off, and it's as hot now as it was back then.