We're both straight. In fact I'm getting married soon.
Went to a swimming pool when we were about 16. My and my twin went to get a shower and all the usual pre-swim stuff. Both of us went to the bathroom as well. Bathing Shorts were on.
He went into the cubicle whilst I took a leak.
When I was finished I noticed his shorts on the floor underneath the cubicle and feet pointing the wrong way. (all guys use the urinal not the cubicle to take a leak. So I waited a few minutes out of curiosity).
The floor was wet giving a perfect reflection upwards. And I saw his thick huge cock standing to attention. He is my twin so we have identical sizes (hence the compliment!).
Sure enough he starts to jerk off. I instantly felt guilty but couldn't stop watching. After a few minutes of on and off jerking he was being as quiet as possible. Then he started to speed up and stopped. Followed by a huge squirt of cum all of which was in almost total silence. I'll give him credit. Haha
So I pretended to walk back into the bathroom and asked him what is taking him so long. Then asked if he noticed that the floor had a perfect reflection. He didn't click.
Once he left, I went straight in as well to shoot some cum. Couldn't resist. I had to. Bit weird being turned on by watching your own bro crack one off without him knowing!
Anyway. To this day he has no idea I watched him spunk from jerking his huge shaft. The same size as mine!
Anyway. Both of us are engaged to girls now. But good times.