Hi i'm Seb and I have been living with my girlfreind and her sister for the last two years and all had been pretty tame until the xmas just gone.

My girlfriend Nat is spanish and is a fiery woman in the bed room. We are both sex addicts and it was rare for us to go longer than a day or two with out it. Her sister Katarina or Kat as i called her is the more timid one and although she is to die for sexy she is single and seems happy that way. Atleast thats what i thought.

On boxing I had come home from a big luncheon where I had left Nat to visit her Pearents. I had thought that Kat would be with her pearents too and that I was coming home to an empty house. I wlaked in and stripped down to my boxers as it was stinking hot and Nat had made me where the presents that her perents had giving me inculding jeans and a jumper. I was about to enter the bathroom when i heard a something. I stopped in my tracks and listened more intently. I heard it again, a little moan coming from the bathroom. The door was open ever so slightly so i knelt down and peered through the gap. There in all her glory with one leg up on the bath was Kat rubbing her clitty and caresing her breasts.

My hand instinctivly moved dowb to my cock which was already one the rise and grabbed it and started to work it. I continued to watch as she looked at her self in the mirror while continuing to play with her self. Her momentum grew and her hips where flexing back and forth into her hand. Then she started moaning louder and panting "fuck me fuck me" over and over. I was now rubbing my cock into a frenzy as I watched her and i knew i wasnt going to last long at the pass i was setting. Then she said somthing that changed everything. Still panting fuck me she then started to add some phrases. first she siad "fuck me like you fuck my sister" then "i'll show you how timid i am fuck my ass SEb".

My hand froze on my cock as I realized she was fatasizing about me and then started stroking again when I heard her say my name. By this time she had the fingers of one hand rubbing her clit the the index finger of the other hand up her ass. Nat had never let me fuck her ass even though I had asked 100 times. I was ready to explode right there and I started to moan too. She heard me and glanced over to see my outline between the crack in the door cock in hand. She froze, as did i but then she just turned to face me and kept going. I took her lead and prized the door open some more and kept going also.

There on my knees at the entrance to my bathroom while my Kat took herself over the edge I came in a grunting growing mess all over the floor. Kat was shivering and shaking through her own climax as she watched me pump every last drop from my aching member. We stayed in silence and all I could do was smile foolishly. Was this going to end my relationship with my girl friend? Was this going to go any further with Kat a thousand question that cant be answered today but can in the future.......