She said that if I ever notice them watching that I should ignore them as they are harmless.”Sue jumped in with, “It kinda turns me on knowing tha... they watched us get off. Does it do anything for you two?”“It doesn’t do anything for me or bother me as long as it doesn’t bother you girls,” I offered.Doreen was quiet for a moment and looked deep in thought then grinned wildly before saying, “It doesn’t bother me, but maybe we can use it to our advantage. They do have a nice pool, and I’d love to. You can fuck me as hard as possible, and I’m ready to be your slut. What say?”“So, you want me to fuck you! But I don’t feel it’s right. You’re my sister.”“Nothing is wrong, babe.” I touched his crotch and felt a big boner. “You are so hard already. Now I want it even more badly.”I pulled down his trousers and underwear slowly. Inside was a thick brown dick with minimal hair. It was completely hard and erect. I grabbed it gently and started stroking it. I could feel it pulsating and getting. There she stood, fully exposed, naked, with tatters of fabric hanging down. Her breathing increased in tempo, and I could see a bit of moisture just below her landing strip. “Good, she is getting turned on,” I thought. Once again I started to slowly slide my fingertips over her body with a featherlike tough, while with my other hand, I slowly undressed myself. Once naked, I moved closer and moved my mouth onto her lips, slowly opening it with my tongue. I did not need to make an effort as. We both just liked the feeling of being naked outside and swimming.We are very close, my sister and I, being twins and all. Our mother would sometimes joke that we were conjoined at birth and that’s why we’re so close, like we have a psychic link between us. Anyway, it’s really no big deal that we saw each other naked a lot and that’s probably why.So we’re a bit older now and we haven’t skinny dipped together in years. We actually haven’t even talked about it at all until this one afternoon.