My sister and our family dog

I caught my sister fucking the family dog.

7 o'clock Saturday morning I got home from a friends place we had played D and D all night and I was ready to get some sleep.
My parents had just left to go shopping and I had met them on the way out.
I came in through the carnage and locked it behind them. The only other person home was 15-year-old sister Tammy, and she never got out of bed before noon.
I was just heading for my bedroom when I heard a noise from the kitchen. I went into the dining room and looked through the fold out shutters. between the kitchen and dining room there was a wall with an opening like a counter a put the food. You can close it off with these wooden shutters. Tammy was at the back door she was wearing a robe and calling our dog Rex. Once he was in the house Tammy dropped her robe. Now a shirt covered her top and she was naked from the waist down.
She played with Rex and led him over to the mat on the floor where she got on her hands and knees.
Rex was really excited and started licking her out. She started moaning with pleasure from his tongue.
Then Rex mounted her and she guided his cock into her pussy.
He fucked her fast and then stopped with his cock buried in her cunt. He tried to get off of her, and she had to keep him still while his knot went down.
I walked in taking pictures and letting her know what I was doing. Rex got off of Tammy and started to drag her across the floor I grabbed him and held him still. Tammy was crying. As I held Rex I asked, "Why did you bother wearing a shirt?"
"He holds onto me with his front legs and scratches me with his claws."
I looked down at her and said, "You know while your down there."
She responded with "You must be joking," I flopped my dick out and. "Unless you want people to see those pictures."
Without a word Tammy started sucking my cock. As she did it, Rex's cock popped out of her pussy, and he went back to licking her cunt.
Then Rex jumped on her back a second time and rammed his cock straight back into her pussy. As Rex fucked my cock came out of her mouth and I shot my load all over her face. I then got into a better position and watched Rex's cock as he fucked Tammy. I watched the knot enter her and a little bit of cum leak out. I reached under her found her clit and rubbed it. As Tammy orgasmed, she fell forward and Rex popped out of her.
I helped her up took her to the bathroom and then let Rex out I then helped her wash herself sand got her to her bedroom before our parents got home.
That night I had a wank looking at those pictures on my phone.
Once Tammy realized I was not going to show our parents the pictures she came to my room and started trying to bribe me to erase the pictures.
I had her suck me off. Then I had her let me go down on her.
The following weekend Saturday morning she didn't have to sneak around as soon as our parents left, we were both in the kitchen and I got to watch Rex fuck her.
I came in with the robe I told her to take it off I would get Rex. She did I walked up to her, and we kissed I got my hand between her legs and using the side of my hand I rubbed her pussy.
Then she knelt on the mat and I called Rex. He ran up to Tammy and licked her pussy before mounting and fucking her. I lay on the floor beside them and watched the action close up.
Tammy wanted to know what I found so interesting down there, so I borrowed her phone and recorded Rex fucking her the second time. Then I showed her what it looked like from my angle.
I then let Rex out I found her on her back fingering her pussy while watching the video. Her pussy was open the inner lips poking out and parted dog sperm ran down the crack of her arse.
I got on top of her and fucked her pussy on the kitchen floor. Tammy didn't say anything she just lay wrapped her legs and me and moaned as I fucked. I dropped my load in her pussy out. I couldn't believe I had lost control like. Tammy looked shock she looked me the eyes and "Don't ever cum in my pussy ever again. Next time pull out before you cum."
Next time, she wanted to have sex with again?