To start with I will just say that my sis and I have always been best mates, and we always will be.
A few years ago, when I was 15 I used to have soccer practice after school every Monday, and one day I came home and my sister (who was 13 at the time) said 'Mom and Dad have gone out and they will be back later'. I said that was fine and that I was gonna go have a shower.
After I got out of the shower I went into my room with only a towel on and saw my sister in my room looking for her headphones. 'Oh sorry' she said 'I was just...'. 'No its fine' I said. Me and my sister saw each other naked all the time so I had no trouble changing in front of her.
I took off my towel and my sister just stared at my cock. 'Oh my god, it's huge' she said, I asked her if she wanted to touch it and she said yes. She grabbed it with both hands and I started to get hard right away.
She began to stroke it until I came, some cum splattered over her face. 'Wow, that was wicked' she said, I asked if she wanted to be touched by me and she said that she would. So I laid her on my bed and began to remove her skirt, I took off her knickers and saw that she still had no hair on her pussy at all. I said 'wow nice pussy, so tight'. She giggled and then asked me to touch it. I began to rub her clit until it became hard and then I stuck my finger into her hole and began to move it fast, in and out. She started to moan and told me to go harder, I said 'yeah you like that don't you, you like my finger in your tight pussy', she said that she did and she began to scream 'yes I love it, I love you'. After a few minutes she came and then just lay there pantng for ages.
When she recovered she said thanks and then got dressed and went to her room, we haven't done it again since but I will always remember that great day.