When I was 18 years old, my sister Becky came out as a lesbian. She was 22 at the time, and it caused a big rift in our family. But she and I had always been close, so I supported her and we both became estranged from our family. This brought us closer together than ever, and eventually it led to a sexual affair.
A couple of years later, when I was 20, I transferred to a college in her city and during that summer I moved in with her and her new girlfriend, Tammy. I had never thought of Becky sexually, but after her revelation I kept imagining her with women. After I became sexually active, I started comparing her more and more to women. Checking out her soft body more and more, and eventually I started even jerking off to her. I never imagined that anything would happen between us, but this all changed when I moved in with her and Tammy.
Becky and I are very similar in appearance, taking after our mother's looks. We both have our mother's blond hair and brown eyes, and people who meet us both often remark that we could be twins. In the past Becky would usually respond by pinching my cheek and saying something like, "Yep, this is my beloved baby brother!" In the past this never bothered me, but after I became attracted to her sexually I would get flushed and usually try to hide any sign that her getting so close to me usually gave me an erection.
Becky had started to date Tammy and they moved in together a few months before I arrived that summer. They had an apartment downtown close to the entertainment district. A friend of theirs had moved out so they were happy to have me come in and help with the rent. I knew Tammy from pictures and social media, but we hadn't met before. The second we met in person, she gushed, "Oooh Becky, he's adorable! He looks just like you!" It felt very welcoming and I immediately liked Tammy, but I blushed again and the girls poked fun at me.
Now Becky and Tammy were very different physically. While Becky is blonde and has always been a bit on the plump side, Tammy was a brunette and quite thin, almost androgynous. She has short black hair and small firm breasts. She would often go braless, even when wearing tight tops. But she was very pretty, with a bright face and personality. She was very forward and good at getting people out of their shell. In contrast Becky has large soft breasts which hypnotically sway with every movement she makes. I remember she was sometimes embarrassed by her breasts and plumpness, but I always found her to be alluring and sexy, often yearning to caress her. I imagined she would be delightful to fuck, soft and wet and moany. Meanwhile Tammy gave the impression that she would be a hard fuck, her tight body taking punishment as well as dishing it out. I suspected that Tammy was the dominant partner, and this would bear out after I got a closer look at their relationship.
After I moved in, for a short while the girls tried to be demure about their sexual urges. They would retire modestly to their bedroom to make love. But pretty soon I started hearing more and more moaning from their bedroom, especially from Becky, and it soon became necessary for me to go to my bedroom and jerk off. It was hard not to think about what they did to each other. Eventually, we all became good friends and they became more open, kissing and rubbing each other a little in front of me. Still pretty innocent stuff, but more and more obvious. I noticed that Becky was still pretty shy in front of me, but sometimes I caught Tammy looking at me for a reaction. One rare day when they were both out of the apartment, I couldn't help myself and snuck into their room. I sniffed their dirty panties and even opened their bedside drawer and sniffed and sucked their dildos, imagining them fucking each other's pussies with them. I wondered if they thought about me in the room next door, but I figured I was dreaming. Still, after that I went to my own room and masturbated to an amazing orgasm.
Soon after that we all went out for drinks together with a group of their friends. Though they mostly hung out with a group of lesbians and gay guys, we all got along and they treated me like a bit of a straight mascot of the group. That night in particular Tammy was very intense. I caught her looking at me a lot, and she was even a little touchy-feely on the dance floor. When it came time to go home, she insisted that we close out a bar near the apartment with a few more rounds of drinks, just the three of us. Even Becky got pretty drunk, and was unusually loose and giggly.
In the elevator on the way up to the apartment, Becky and Tammy were hugging, with Tammy basically supporting Becky to keep her from falling. Suddenly Tammy gave her a deep kiss, which Becky returned eagerly and even moaned a little. I couldn't help but stare at them, and though I felt myself getting hard this time I didn't try to hide it. Tammy broke off and glanced down, noticing my erection, but didn't say anything. Instead she reached over and touched my arm, almost as if steadying herself, but she caressed me gently. This made my cock get fully erect and she glanced at it again, this time looking up at me and smiling mischievously. I returned her smile without saying anything.
When we finally got into the apartment Tammy suggested we have another drink and smoke some hash. So we all sat on the couch together, me on the end with Tammy next to me and Becky on the other side. The whole time Tammy couldn't sit still and kept rubbing her bare legs against me. We had gone out dancing and were all pretty sweaty, so the room filled with our mingled body odor. She kept leaning over and hugging Becky, seemingly making a show of touching her and showing her off to me. Sometimes they would kiss a little. To my surprise Becky seemed not to notice or mind that I was right next to them. For my part, I made no attempt to hide that I was looking at them and didn't try to hide my erection, though it took a lot of willpower not to rub myself. I wanted to desperately, but didn't want to ruin the mood. It became even harder when I would hear Becky occasionally let out a little moan.
finally Tammy broke off and turned to me. She reached over and pinched my cheek like my sister did and said, "You're so cute. Becky, your brother is so cute!"
Becky raised up a little and looked at me, then sank back. She closed her eyes like she might fall asleep, but exhaustedly she said, "Yeah he's cute, all right"
