Niece's Panties

My wife's 14 year old niece was staying with us for a week over the summer holidays. One Saturday morning my wife and niece were out shopping when I went to load the washing machine. I noticed a pair of niece's white panties and thought 'why not'? Five minutes later I had shot my cum into them. The thought that a few days later she would be wearing them again was so horny but I only did it the once.