In addition to that let's face it; Mark and I were both sexual deviants, and got off to no end on the fact that we were brother and sister and breaking the rules every time we got together. The sex was always hottest when I was telling Mark to fuck his nasty sister, to make her suck his cock. Part of me already knew that I wouldn't ever want Mark to not be my brother, that even if we went further part of me would need him to still be that for me. Mark on the other hand was upset when I called him little brother yesterday as if he...