Mike and Mark were twin brothers. Their bodies are as different as can be. Mark is broader and has more muscles and is taller. Mike was short and did have some outline of muscles, although not that much definition. Mark was also more athletic and Mike was smarter.
Mark didn't want Mike to be frail so they signed up for a gym membership and went often. One day they stayed a little too late and had to shower in the gym showers. Mark and Mike had never seen each other naked at this day and age of 18. Doing so seemed a bit weird.
When they entered the locker room, there was an eerie silence in there that seemed no one was in there. And it was true, everyone who had used the locker room had left and it was just Mike and Mark in there.
Mark started to undress without much thought. But Mike had a secret. He had a secret crush on his younger brother by 2 minutes, and when he was undressing Mike felt his cock start to rise. Something about Mark's toned smooth arms, and his tight ass made Mike all excited. He knew this was wrong but he had always wanted to see his brother's cock.
As Mark pulled his boxers down to reveal his jaw dropping cock. Even though they were brothers Mark's girth was much larger than Mike's.
Mike had trouble looking away. Finally he caught himself staring in time before Mark realized this.
Now the bulge growing in Mike's pants started to really stiffen. Mike said, "Hey, are you going to change or what we got to get going in a little bit."
Mike said, "what. Oh yea ill meet you in the shower room in a sec."
With that Mark left and with his long cock bounced and forth as his sac swayed from side to side.