Just a silly story, part 2

It had just about driven me mad, locked away for all those weeks, seeing only my family. I was as horny as hell, I seemed to be walking around with a permanent erection. The house today was empty, I wandered into my younger sister's room hoping she had left something lying around, lucky today, two pairs of panties. I picked a pair up, I couldn't resist sniffing them, the beautiful aroma of her pussy was still just evident. I couldn't help myself, I had to try them on, not for the first time, they fitted to perfection. I then tried on the other pair, these were dark blue and her aroma was far more pungent. It crossed my mind that she had been masturbating in them, I don't know how I stopped myself from having a wank in them. I heard a sound downstairs and decided I had better get out of her room. If she caught me again she said she would tell our mother. My older sister was far more accommodating and would let me help myself to her underwear, but she is away at university. My younger sister is just out of school knickers and into fancier underwear and far more private. The last time she caught me in her room I had her dark green knickers on, she told me to get them off and get out of her room. I did as she said, but I know she saw my cock, as I walked out she let her hand brush my arm. I went back to my room and sat on the bed, a minute later there was a tap on the door, she came in. She said she had just come to say she was sorry for snapping at me, she knew I liked to cross dress and that I loved panties. In future if her panties were on the floor I could help myself. This was all well and good but I wanted some male company and the panties. A few minutes later my sister shouted to say she was going out and see me later,I went back to her room, both sets of panties were on the floor. A little yellow post-it was stuck on the blue ones with a note which said, "Have fun, love Gilly". So now both my sister's new about my xdressing, somehow I didn't care, in fact it felt rather good. I decided I would go into college and hopefully see Mr Chambers, I put on Gilly's dark blue panties under my trousers. Hopefully I could get Mr Chambers by himself, when I arrived I went straight to his room, sure enough he was there, and by himself. He waved me into the room, I could feel my cock growing as we sat talking, I so wanted him to make a move. He said he had been hoping to see me and how much he had enjoyed our last time together, I had made sure he could see my cock in the shower and I had worn his wife's underwear, he had wanked me off into them, then his wife had put them on when they had sex. He asked me if we could do it again sometime. I agreed, but I said I could do with a little pleasure right now. I made the first move and gently rubbed his groin, oh wow, his cock shot up, I took it out and began to wank him. At last he made a move to me, I let him see the dark blue panties and told him they were my sister's and I wanted to cum into them. His touch was very light as he played round my bell end, then I could feel my juices rising, my cum was all over Gilly's dark blue panties. When I got home my sister was in the kitchen with our mother, they both smiled. My mother asked if I had any washing needed doing, my sister smiled again and walked away.