My perants went on vacation , and me and my brother had the house to ourselves for 2 weeks. The first day they left, I was sitting on the deck near our pool and my brother surprises me with wine and we decided to get drunk. It was such a hot day and a few glasses of wine later i dared my brother to jump in the pool nude. He laughed and said made me agree i would do it if he did it. So he strips off infront of me and jumps in nude. After he jumped in i was laughing so hard because i wasnt going to jump in at all. But then i felt bad so i told him i would do it. I stripped off and jumped in with him. We spent like an hour drunking naked together in the pool. And we started talking about how good it would be to be a nudist. So we decided to make it a compeition. Who would last the longest not putting clothes on. So the first few days were cool. we would just do our normal thing and hang out in the nude. And it was the 4th day my perants were gone when it all happened, I woke up and was having my morning shower then my brother walks in the shower and turns the other taps on. our shower is a double so 2 people can shower at once. I was like whatever. he starts to shower and i couldnt stop gigglig because he had the biggest erection. I asked him if i made him excited in a joking way. He laught and replied maybe i do make him exciited. He then asked to feel my boobs, I dont know why but i said go for it, and he started feeling my boobs, and we started to feel each other up. I stopped because it didnt feel right but then he kept touching me softly and i lost control. He started to finger me and we fucked in the shower, And we spend the rest of the week and ahalf we had to ourselves having sex every day and night. I feel so guilty. Im 19 his 21. I love the sex though. We constantly hook up now. Whenever we get a chance i was a virgin before this as well. Im such a fucked up girl. I want to stop but he is so addictive.