Hello there, i am a 4 years younger than my sister. We were living at home and i had been using her panties to assist me with my orgasms for a while. Feeling the dirty panties around my stiffness would make me cum quickly. One day i was laying on my single bed with my trousers down and stroking. I thought the house was empty. My bedroom door and she just stood there. I don’t know why I didn’t stop. I carried on. She said nothing. Just looking at my cock. She was just wearing a tshirt and jeans. Nice big boobs After a couple of strokes i came. Not sure if i saw her smile but she turned and walked out. She never spoke about it and neither did i. Thought about very often.