I love this site! This was my first experience with a boy, and I got off thinking about this for years!
I was helping my older sister move into her college apartment with her boyfriend Rob. Cara had driven back to her old apartment to get more things, when Rob started rubbing his shoulder complaining about pulling a muscle moving the chair. I moved behind him, and start to gently massage his bare back, and he sighed and told me how good it felt. He laid down on the sofa on his tummy, and I sat just below his tight butt, and started to give him a full back massage. After a few minutes, he flipped over and asked me to massage his chest. I rubbed his pecs and hard abs, and saw the bulge in his shorts was definitely bigger. As I was rubbing his stomach, he took my hand and placed it on top of his bulge.
I had never felt an erection before, and was amazed at how long and hard it was. I rubbed it and squeezed it through his shorts, and he was laying back with his eyes closed. He raised his hips, and pulled his shorts down to his thighs, exposing himself. I stared at it in disbelief. It looked so powerful and strong. It curved slightly upwards, the head laying just shy of his bellybutton. It was darker than his pale skin, and his balls were big and low hanging. I ran my index finger along the shaft up to the head, and he squirmed. I kept doing that, until he whispered for me to put my hand around it and rub it. My fingers barely met when I did, and I slowly started to jerk him off. I watched his balls move up and down with each stroke, and cupped them in my free hand. I was surprised how soft his sack was, and how his balls moved around so freely. He whispered for me to go faster and I did. I saw the clear liquid drop at the tip, and thought he had orgasmed, so I asked him if he was through, and he just shook and head and said soon. As I started to go faster and faster, his hips started to thrust into my hand. And he started to breath hard. His chest and stomach were heaving as he panted. Suddenly he threw his head back, arched his back, and without a sound, it happened. The clear liquid covering his head was replaced by spurts of white. The first two landed on his stomach, the next few just oozed out and onto my hand. He looked up at me and smiled and said thanks.
He looked down at the mess on his chest and pubic hair, and asked me to grab some toilet paper from the bathroom. I rubbed the mess off my hand onto his chest and hopped off.
He cleaned up as I watched the goo smear into his stomach. His dick was softening curling back to a flaccid state.
He pulled his shorts up, winked at me, and told me that was the best back massage he ever had.
That night, I slept on that couch, as Rob and Cara slept in her room. I could hear them having sex, and I masturbated thinking about Rob's long hard dick sliding in and out of my sister, like it slid in and out of my hand. It was the best orgasm of my life.