My sister was only about one year older than me, but for as long as I can remember she always liked to boss me around.
It was the summer when I had just finished high school and she was back from her first year at university.
My parents' room was on the other side of the house, so I had got used to being the only person using the bathroom, and was in the habit of not bothering to lock the door, and sometimes even leaving it open.
One evening I in my pyjama pants, standing at the wash basin brushing my teeth, when I heard someone behind me.
I half turned, and saw that it was my sister.
"Oh, I didn't think anyone was in here," she said.
She was wearing a white t-shirt with a pair of light cotton shorts, and my eyes were immediately drawn to the shape of her tits, the nipples clearly visible through the fabric of her top.
Even though she was my sister, I started to get aroused, and in another moment my swollen cock had slipped out of the gaping fly of my cotton pants.
Just as my eyes had been drawn to her tits, so she gazed at my staff, as it briskly pulled itself fully erect.
I had a feeling that I shouldn't have been looking at her like that, and that I should have turned away from her, but because she had not reacted in shock, or even tried not to look at my arousal, I stood still, aware that all the while I was still exposing my cock to her.
I heard her catch her breath, then she made as if to leave. I turned back to the sink, trying , with some difficulty, to tuck myself back into my pants but then she hesitated. She shut the door, and leant against it.