Our parents just forgot us for a week at Grandma's, and we're not very well-behaved or obedient, we're still quite wild and curious to discover our sexuality. We got the same bed and we were left alone, so out of curiosity and lack of internet access we had to talk with each-other. I was dressed kinda skimpy, a loose, transparent blouse... The story is older than time, being alone with each-other like this... it wasn't too important for us that we are, in fact, step-brother and step-sister. We began to see each-other as a source to satisfy our own sexual curiosity. He wanted to see My Boobs, to touch them, claiming that it's the first time in his life he touches real Boobs, so he groped them a bit and played with my nipples. I let him to do it because it was feeling so awesome for me, I never had my boobs touched like he was touching them now, it was an extremely arousing massage! Apparently he felt the same, aroused, his boner became visible soon and he was kinda ashamed, but proud... but ashamed! I asked to see it, and it was sooo big! I started having naughty thoughts about that hard penis, I actually felt worshiped, I mean he got hard immediately after touching me, I must have quite an influence over him! I didn't care anymore that he's my step-brother, I undressed quickly and asked him to come closer, so I could suck his cock. Well, I'm not so naive as I pretended to be, I DeepThroated all that cock without trouble (well, maybe in the beginning, a little). I was just horny and wanted to do something extreme, something that would outrage anybody, so I was showing him my interest and love by sucking it in creative ways and fondling the tip with my lips. We decided to fuck, it happened so very fast, it was more an impulse than a rational decision, however, I don't regret any of it! He fucked me hard (I'm starting to think he's not so naive either) and made me cum more than once. I felt those orgasms to the bone! Now it was time to make him happy, and I did that by rubbing it really fast over my huge boobs that he loves so much! The most taboo thing for me it was that I tasted his cum and I liked it!