It all started one night when I was feeling very horny. I decided to creep into my sisters bedroom to sniff her knickers. I always did it as I had a fascination with my sister. My sister was 17 and I was 18 at the time, she was slim and was very pretty. I walked into her room to grab a pair out of her washing basket, thinking she'd stopped out at her mates, when all of a sudden I heard her moving in her bed and my heart w...