Never did this with anyone else
My brother was two years younger than me. When he was about 13, his attempts to see me naked increased greatly. It was a hassle but not annoying.
I started to let him catch me partly undressed. At first only my bare back without a bra. But when he started hiding in my room, I let him see more. Little by little he had seen almost everything. One day, I left my bedroom door open and pretended to be asleep. I only had a tee on.
I heard him come up the stairs but never heard him enter my room.
I felt him lift my tee. He tried to open my thighs with just a little pressure. I resisted and he stopped. Next he slipped his hand up my tee and started to rub my tits. No one ever did this before. I liked it but he stopped and work my teeshirt up higher. He took a while because I was laying on it. I helped by lifting up a little. When he tried to get it over my head I moved my arms to help.
He said he knew I was awake. I acted like I was waking up. But he was not fooled. I was going to get mad and start screaming but he asked if I wanted to see his dick. Yea!
He only lowered his pants and underwear enough to see his penis. It was hard, not five inches long. He started to feel my thighs and I let him. Soon his hand was between my open legs. He climbed on the bed. He sucked on my tits while moving one finger inside me. His dick was rubbing against my hip. He exploded, shooting jizz on my thigh. Another first for me. He never stop fingering me. He tried to mouth kiss me. I gave in on his second try. I went over the top. It was the best ever.
He asked if I had come. I told him, yes the best.
I needed some off time but wanted to do it again only I wanted to see him shoot his jizz too. I did that every day.
After that, I was often naked when we were alone. That always got him going. When others were around, I flashed him when they couldn't see.
It never really stopped it just died out.