The shed

Finding a sexret door inthe back of a shed on my property, I found a new past time.

Recently I bought a small house on a quiet Street. The day after I moved in I was just admiring my backyard which is a decent size and the one corner is a shed-like building. Which is set onto a tight grove of banana trees. So tight together that a person can't walk around the shed.
As I open the door I notice the inside is painted flat black. Walls floor and ceiling . So I figure whoever had this place must have used this as a darkroom for photography. There is a work bench along the back wall and a sink on the side wall. No windows anywhere.
As I was exploring the inside, I noticed what looked like a hidden door. Took me awhile but I was finally able to figure out how to open it. When I walked in I had to turn my phone's flashlight on it was so dark. First you walked in a narrow doorway then four feet in was a ceiling to floor black curtain. On the other side of the curtain was one sole window and a chair. As I walked over to the chair I noticed on the back wall was the only window in the whole shed. Looking out of it  I had a clear view of the house behind me, about twenty feet away,  and a window that looked like it was a bedroom window.
I was just getting ready to leave when I noticed someone going into the room. It was a girl who looked to be between 13-15 years old. Long blonde hair that came down to the middle of her back. Fair complexion and petite but nice tits. Following her was a small boy. I figured he must be her kid brother. She sat on what I'm assuming was the foot of the bed. He moved till he was in front of her. Then she reached out and unbuttoned his jeans and pulled them and his underwear down to his ankles. Steering straight out at her face, was his cock. Which looked like it was three inches hard and thin. Maybe the size of a large thumb. Without any hesitation she leaned forward and took his cock in her mouth. As she slowly moved her head back and forth, she took her hand and started playing with his balls. Rolling them with her fingers as she worked his rock hard shaft. As she started I decided to take a seat on the metal chair sitting there.
You could tell that he was enjoying himself, his head was tilted back, eyes closed and you could see he was breathing heavily. Then as he reached out both hands and took hold of her head. He started pumping faster. She pulled back and took his cock out of her mouth. Said something then wrapped her fingers around his shaft and squeezed. Holding it tight she stood up and made him sit, then she let go of his cock and undid her own pants. Slid them down along with her pink bikini panties. Grabbed his head and pulled him towards her well trimmed pussy.
The boy stuck out his tongue and from bottom to top. Licked her till she pushed him back. From my vantage point all I could see was his hips and penis which was still sticking hard as ever sticking straight up. The girl worked herself with her knees till her pussy was right above his cock. Then without any presentation she impaled herself on his cock. Worked herself fast and hard up and down till all of a sudden she slammed down then gyrated her hips . After a minute she eased up as his cum dripped out of her.
With that the show was over. She made her little brother leave. Then wrapped a towel around herself and left the room.
Realizing I also had a hardon from hell. Just from watching, I got up and as I left. Knew I would be back.