The first thing I heard when I came inside was my sister Kylie yelling at our Dad over the phone. She said she wasn't going to stop hanging out with "Those people -- they were her friends," and that she hated him. My Dad and my little sister have always butted heads but this seemed like their worst fight in awhile. I sat down next to my sister and told her she shouldn't worry about what Dad thinks of her friends -- she should just be more sneaky about hanging out with them. I told her there's a ton of stuff I've done that Dad doesn't know about. I calmed my sister down with a back massage and then joked she could return the favor by blowing me. She just laughed and called me a perv, then she looked in my eyes and saw I was being serious. My sister's first lesson in secrets started with a blowjob, and I promised Dad would never know...My little sister sucked my cock so well... I could tell she must have learned a lot from those "Friends" Dad didn't want her seeing anymore. It didn't matter what Dad thought -- her big brother approved and knew how to keep a secret. I told Kylie we needed to fuck -- and she agreed. The moment I slid my cock inside my little sister's dipping wet pussy, I knew we were doing the right thing. I could feel us growing closer together with each thrust. I've always loved my sister, but as she rocked back and forth on top of me I knew things would never be the same...My sister bounced on my cock until I couldn't take it anymore. I could barely resist the urge to cum inside my little sister's pussy, but I knew I had to hold back. I pushed her off and fucked her from behind as hard as I could. Then I turned her around and blasted a huge load in her mouth. I was dizzy, I could barely breathe. My little sister asked me one last time if I was sure Dad wouldn't find out about this, and I said yes. There was one other thing I was sure of...I just had the best sex of my life -- and I had to keep it a secret.