Tonight I found that my sister had been wearing my favourite knickers all day to work, they were just lying there in her washing basket when I did my regular check after her normal shower routine. God I love these big knickers so much that I had an instant hard on and had to take them to my bedroom, quickly strip off and then slide into those soft gorgeous knickers of hers straight away and I swear they still felt warm to me but that’s imagination for you!  I couldn't get my mind off the image of my sister wearing them only moments ago and then I did something on the spur of the moment and I've never done before, I left her knickers on and then put my dressing gown on over.  Then with a huge hard on I went back down the stairs to join my sister in the lounge wearing my dressing gown and just her blue knickers.  I got a few comments about wearing my dressing gown but I just said I was waiting for the hot water to heat up again to have a shower.  God it was such a turn on to sit there so close to my sister and she hadn't a clue that I was wearing her underwear .