Stroking while watching her sleeping

When I was about 12 I was at a family friends house spending the night. It was me and another kid same age and his sister who was about 11. After the adults went to to bed we started playing in the back room so we wouldn't wake them.

We were just playing video games, but somehow it turned into "pants" each other (pulling each others pants down). Nothing sexually at first but that soon changed. I had the idea to turn the light off and pants his sister when she couldn't see us. I told him to stand by the light switch and turn the light off, I would pull her pants down and then he would turn the light on to embarass her.

The plan worked well, the light went out, and I pulled her pants down, and told him to turn the lights on. When the light came back on she was standing there completely bottomless, I had pulled both her pants and panties down. Her brother was just laughing and teasing her, but I was turned on. she had just started to grow pubic hair, and you could see the little patch that was there. I was instantly hard. I told him to turn the light off again, and tried to help her pull her pants back up, while trying to touch her vagina at the same time.

After she pulled her pants back up she left the room and went back to her room becuase her brother was teasing her about her pubic hair. We went back to playing video games for about another hour and then decided to go to bed.

We went into his room and started to get ready for bed, I told him I needed to go to the bathroom and left the room, as I walked to the bathroom I noticed that his sisters door was opened a little and I peeked in there. she was fast asleep. I snuck in, and closed the door behind me. She was laying in her bed covered up. I slowly crept to her bed and pulled the blanket back, and she was wearing a little t shirt and her panties. Seeing this my penis started to get hard again. I was afraid that I was going to get caught but I had to relieve myself. I unzipped my pants and pulled my penis out of my zipper hole, and started to stroke myself while watching her sleep. I very lightly touched her vagina over her panties as I stroked. It didn't take long for me to start cum. I tried to shoot it onto her panties but it didn't quite make it and landed on her bed in blankets and some of it on her leg. I quickly covered her back up and zipped up. I left her room and went back into my friends room and went to bed.

The next morning I didn't say anything, and she didn't say anything so I assume I got away with it.