My parents divorced when I was fifteen. Mom and I have been pretty close since then. She was always cool about things like my seeing her undressed. Just sort of casually, like going from the bathroom to her bedroom after a shower, although she never really walked around the apartment that way. After I turned eighteen though, she started to be a little more uninhibited about doing that around me, like walking into the kitchen after her shower with nothing on to get a cup of coffee. Not that it bothered me, since I had seen her undressed before and was used to it.
One day last month, she happened to stroll from the bathroom and into the living room nude, where I was sitting on the sofa. She just smiled and looked quite nonchalant about it, and asked me why she never got to see me nude around the apartment. Typically I covered up with a towel. I just said that I guess that I didn't want to embarrass her. She assured me that she wouldn't be embarrassed if I felt like doing that some time, using right then as a good example. Kind of reluctantly I agreed. I was sitting there in a t-shirt and shorts, and was barefoot, so it was not much of an effort to get undressed. It was kind of fun, both us sitting there naked together like that.
As I kind of feared, though, after a few minutes I started to get an erection. Not that my mother looked shocked or anything. Actually, she seemed amused by my response, which made me feel a little less embarrassed. I was surprised, however, when she said that it was okay with her if I felt like masturbating right there in the living room, and suggested that maybe we could both masturbate at the same time. I have to admit that I was hesitant, but under the circumstances it did not seem like such an extraordinary thing to do. So I started to stroke my erection and she started to finger herself. We sat there smiling and providing each other with mutual encouragement. After several minutes I ejaculated and she had an orgasm. It really seemed like the most wonderful experience to have together as a mother and son. Since then, mom and I have masturbated together on numerous occasions, and always with great results.