Last week my wife and I invited her sister over to hang out by the pool. She showed up a little late so we were already in the pool cooling off when she arrived. Her sister shows up in a really small and revealing white bikini. She is about 3 years older than us, very petite with a nice ass and small boobs and very attractive. So I get out of the pool and go lay on my chair, they’re swimming around for a little bit when her sister gets out as well to lay in the sun. I have sunglasses on so I can inconspicuously look around without being caught. She’s walking right towards me and I glance down and her bathing suit bottoms had been slightly pulled to the side and her a peek of her pussy was visible. I was aroused. She lays in the chair next to me and it’s still out. I’m trying my best not to get a full hard on when she noticed the wardrobe malfunction and without saying anything she fixes it. Some time goes by she gets back in the pool and it happens again, this time my wife noticed and loudly told her to fix it because I was laying right there. She apologized and was slightly embarrassed. My wife offers a different bathing suit and so they go inside to change and I was left alone in the backyard.