I was home alone one day (which is rare since I have a twin sister I share my room with, a younger brother, and then my father) so I decided to look up some nasty porn online. I was only 15 at the time but already I was into some dirty dirty things. My sister and I started having incestuous lesbian sex together 2 years before, and just a couple months ago decided together to seduce our brother (his 14th birthday present). Our dog thunder was in my room with wasn't anything new plus he would let me know if anyone came home while I was distracted (like with masturbation). Well wouldn't you know it, i happened across some animal porn and began to get rather excited seeing women getting fucked by dogs and horses. My pussy was almost dripping when I finally took off my sweat pants and panties and began to play with myself to a video of a big german shephard fucking a skinny little thing of a girl with his big red cock. I was so into this that I didn't notice Thunder( a german shephard) get up and come over to me to check out the new smell in the room. All of a sudden I felt his tongue on my pussy and I had an immediate orgasm. My mind went to one place and one place only, I HAD TO TRY THIS. I got out of my chair and then got down on my hand and knees then turned my head to watch Thunder. His cock was sticking out of his sheath about 4 inches and it looked nice and thick. He bagan licking my pussy from behind and OH MY GOD it was so hot the way his tongue actually went inside my pussy and then continued on up to finish by licking my asshole. I quickly looked at my bedside alarm clock taking note that its still 2 hours before my sister is due home from school (i faked being sick to skip), a good 3 hours before my brother gets home and about 3 and a half before dad would, I was in the clear. I smacked my ass a couple time and said "C'mon Thunder, come fuck me REALLY good boy. Be a good boy and fuck me like a bitch" Thunder had his own ideas though, he continued to lick my pussy and asshole til I had 2 more orgasms and my pussy was literally dripping. Then he mounted me, at first poking my leg, then I felt his cock was lined up properly but was pumping back and forth over my clit which made me cum again. I lowered my ass just enough then I felt his cock hit my hot wet hole and sink at least 7 inches of hot dog cock inside me. I instantly had another orgasm and I wild trying to fuck my pussy onto my dog Thunders cock as hard as I could. Well Thunder must have liked this because he started to fuck me like I would have never dreamed possible. Thunder's cock was deep in my hot teen pussy when my twin sister walked into our room and said "HOLY SHIT, SIS WHAT THE FUCK R U DOING" I looked up out from under Thunder with his cock deep in my pussy looking totally and utterly in exstacy then said to my sister "get naked so I can eat ur pussy then YOU HAVE TO TRY THIS". My sister did like I said and while Thunder continued to pound my pussy with his hot cock I ate my sisters pussy without abandon. Then i felt his knot trying to enter me, hit me once then pressed hard against my pussy, then all of a sudden it was in and OH MY GOD my pussy was so FULL. I felt this hot liguid spraying me inside my pussy and knew I had satisfied my new lover and he was cumming inside his new bitch. He must have sprayed his cum inside me for a good 2 minutes and we were kina stuck together for another 10 or so before his knot came out of me. I collapsed from exhaustion after being royally fucked by my dog and having I dont even know how many orgasms, when I noticed my sister was looking at Thunders cock with big round eyes. "You took ALL of that inside you? How did u get him to fuck you, I want to try" my ssiter sayd to me. I turned and looked at Thunders magnificent cock again and noticed that the 7 inches I thought i felt enter me, was only the beginning. Thunder had a good 10 inch cock about 2 inches thick at its thickest point and his knot was easily 4 inches this and another 2 inches adding to his already 10 inch length. "Ok sis, here's what you need to do first.........."