My girlfriend is a fraternal twin. I had only met Rosemary's sister once before she moved away to Europe over a year ago, and I did not remember her all that well. I knew she was hot, but I had been drinking a bit the night we met, so my memory was unreliable. At first, my twin, threesome fantasies involved my girlfriend being duplicated in an identical twin situation, but that changed once her sister Lily came back home.

Lily recently had a bad break-up with a guy she met overseas and decided to come back home to stay with their mother while she sorted herself out. However, after a few weeks, she got restless and started to spend more time over at our place since we rented a house just across town.

I am happy with Rosemary, and I think she is beautiful, but her sister was very different. Where Rosemary is slender and petite, Lily was curvy and plump. In a cruel twist of fate, they were each jealous of the other's body type. From what I had gathered in stories told by Rosemary and their mother, it had been that way since puberty. From my perspective, it seemed to be an underlying issue for much of the tension that existed between them. To be fair, there was more love than tension, but they had always been competitive with each other and sometimes it got out of hand.

Despite some heated discussions between them I would be forced to sit through, for the most part, I enjoyed having her over. Rosemary had never drunk whiskey in all the time I had known her, but Lily loved the stuff and would listen intently to all my rambling opinions about it while sharing her own as well. It may have been Lily's curves and pretty face that caught my attention first but it was her love of whiskey and our talks that made me see how cool she was. It was after these discussions that I would find myself thinking about her at work.

I had never been a guy that gravitated toward one specific kind of woman. I have varying tastes that have led me to different body types over the years. While I am certainly into curves, Rosemary's distinct lack of them had never played that heavily into my enjoyment of her body. She was a beautiful woman and the two of us had a healthy relationship and a normal sex life. Rosemary was reserved when it came to expressing her sexuality however, she had always been self-conscious about her body and it affected her confidence and ambition. Her imagination for sexual play left something to be desired. I tried not to hold this against her, but sometimes I wanted more from her. Most of the time she was unwilling to shift outside her comfort zone.

All the stories I heard about Lily painted a different picture. Rosemary had always portrayed her to be a bit wild, she was very open with her sexuality and made no attempts to hold herself back when she thought there was fun to be had. I had never heard Rosemary call her a slut but sometimes when she was frustrated with Lily, I could almost sense the word on the tip of her tongue. She would usually end the thought with a few generic sentences about being worried for Lily's safety. While there was nothing wrong with being concerned for your sister's welfare, I knew there were also some of Rosemary's judgments mixed in. In my opinion, Lily seemed to be a smart woman who could take care of herself. I didn't see anything wrong with someone having some fun in their youth, but I would usually keep these opinions to myself since they proved to be unpopular with Rosemary. They had a complicated relationship and I knew better than to insert myself between them, but I admired Lily's confidence despite her self-perceived shortcomings. It only fed into my growing admiration for her.

Lily spent weekends over at our place and would frequently borrow my laptop since it was better than her tablet. Throughout several nights and weekends, she had used it quite a bit but I didn't give it much thought since I trusted her to take care of it. On one particular Saturday, I had been doing some yard work for most of the morning and early afternoon. I was eager to have a shower before I started to relax.

I came up to the deck where Rosemary and Lily were sitting on some lounging chairs to take advantage of the warm sun, both of them looked sexy. Rosemary's back was towards me and she did not attempt to look up from her phone. Lily was sitting up, facing me, and had my computer on her lap. Even in a t-shirt, she looked irresistible and I had mere seconds to admire her voluptuous chest before she raised her head. She looked up at me over the top of her sunglasses and had a look on her face that made me worry she had caught me checking her out, but it quickly turned into a smile.

“The lawn looks good, Jake.” She eyed me up for a few seconds before she dropped her eyes to look at the computer again. I thanked her and told Rosemary that I was going to have a shower. The sight of Lily's breasts stuck in my mind to the bathroom. I could feel myself getting aroused despite my efforts to the contrary. I had less privacy these days and my porn viewing habits had been reduced as a result, I pulled out my phone and searched for a video about a busty brunette as I connected my earbuds. Normally I preferred to use my laptop to watch porn, but given the circumstances, my phone would have to do. I undressed and tried to convince myself it was a coincidence that Lily was also a busty brunette.

I had barely started when I heard the doorknob turning open. I didn't normally lock the door as I was accustomed to living with Rosemary, so I had no time to cover myself or turn off the video on my phone. Lily walked in and caught me mid-stroke. A huge, surprised smile formed on her face as she watched me go red with embarrassment.

“Jesus, Lily. Don't you knock?” Somehow, my first reaction was to remove my earbuds before anything else. I tried to cover up my dick shortly thereafter, but she had already seen everything. I put down the earbuds and used both hands to cover up.

“Take it easy, Jake. I thought you were using the other shower. I'm sorry.” She looked down at my phone before she continued in a teasing voice as she saw the title of the video. “Hmm, does Rosemary know you are in here beating off to 'busty brunette' videos?” I answered her in a distracted tone that Rosemary wouldn't care. Lily didn't wait for me to finish before cutting me off.

"From what I can see in your browser history, you seem to have watched quite a few videos about busty women since I've been in town, but not as many before then.” She had a big grin on her face as she waited for my reply.

“You've got quite a high opinion of yourself. Don't you? How much of my history folder did you look through?” I was annoyed that she invaded my privacy but I was also thrown off guard at how accurate her observation of my porn habits of late had been.

“Relax, Jake. I was only paying attention to the good stuff, like your occasional hentai indulgences. Most of your privacy is safe.” She enjoyed every second of my discomfort as it played out on my face.

“Mind your own business!” I was even more embarrassed at her mention of the hentai, while it wasn't a huge fantasy of mine, I did enjoy it from time to time. There was a time in my life when I would have been diligent to erase my browser history, but I lost those habits during my time thus far with Rosemary. Lily's giggles interrupted my thoughts.

“Don't be embarrassed. I think it's kinky. There's nothing wrong with that.” She laughed quietly before she threw up her hands and backed out of the bathroom. “OK, big guy. I'll leave you to it.” She had a devious look on her face as she closed the door.

I was left standing there with my dick in my hands, feeling embarrassed, but still Lily persisted in my imagination. After the initial shock faded, I felt a little relieved that at least I was jerking off at a somewhat relaxed pace. It would have been worse if I had been furiously pumping away at myself. I felt a bit guilty for worrying about this before any thought of Rosemary, but I pushed this out of my head as I closed the web browser on my phone and stepped into the shower. I couldn't deny how much I wanted to fuck Lily anymore. That smug smile on her face made her look so sexy, I continued stroking myself once the warm water hit my body. I imagined Lily on her knees sucking me off as I climaxed.

I was becoming obsessed with Lily. Her wide-set hips and plump ass seemed to tease me with each step that she took, and that said nothing of her amazing breasts. My orgasm-muddled thoughts were interrupted by a knock on the door.

Rosemary poked her head in the door and told me there was a last-minute shift she had been called in for at work. I should have told Rosemary about Lily seeing me jerking off, but I felt guilty about how accurate Lily had been with her statement about my recent change in porn habits. Before Lily arrived in town I usually chose a video based on whatever thumbnail caught my attention at the moment. Since Lily started spending time at our house, I started to watch big-boob stuff almost exclusively to satisfy my growing desire for her. I also felt guilty for my wandering eyes because I knew Rosemary was self-conscious about the size of her breasts in particular.

I had reassured her many times throughout our relationship that she had no reason to feel inadequate, she was incredibly sexy. The message never seemed to sink in however, if she knew how much I wanted to motorboat her sister's boobs, she would be crushed. I was worried that if I brought up the topic of being caught masturbating, it could lead to Lily spilling the beans on what she had pieced together. If Rosemary knew what Lily had confirmed by snooping in my history folder, I would be in for a miserable fight. I decided that since it seemed like Lily hadn't told her yet either, it was easiest to keep it from her. Rosemary said goodbye and left for her shift.

After I finished in the shower, I changed clothes and sat down to play Xbox for a bit. Lily came in from the back deck and placed my laptop on the coffee table without speaking a word. She gave me a curious look of feigned innocence that I didn't trust, but she continued past me and went upstairs to the guest room where she stayed while at our house. About fifteen minutes later she called down to me that she needed my help. I was a little annoyed but I went to help anyways. My annoyance vanished when I got upstairs.

Lily was on the bed on her hands and knees, facing toward me but angled slightly sideways so I could see her hips and butt as well.

“What do you think?” Her eyes gazed intently at me. She was dressed in a black, leather jacket that stopped at her belly button and was unzipped to reveal a red bikini top that was barely big enough to fit her. She wore a pair of red, tight-fitting booty shorts on her gorgeous ass. I was surprised to see she had put an outfit on just for me, she looked undeniably sexy, I just stared in silence for a moment while I tried to collect my thoughts. My delayed reaction seemed to worry her.

“You hate it. Don't you? I can barely fit my fat-ass into these shorts anymore and this jacket is...” I had never seen Lily look so frazzled before, I suddenly felt compelled to reassure her.

“No, that's not it at all. You look fucking amazing. I mean, uh...” I spoke without thought, but my words pleased her immensely. Her self-conscious attitude faded and a smile crept onto her face that almost seemed to say 'gotcha'.

“I thought you might like my make-shift, anime pin-up girl costume. Since I live out of suitcases these days, I conveniently have access to random stuff like this.” She gave me a very convincing 'come hither' look as she spoke.

“Rosemary would be pissed if she saw you.” I was trying to talk myself down, but I wasn't very convincing.

“That's true, but wouldn't she also be pissed about you jerking off to her sister? Or changing your porn habits to see women that look like me?” She asked this calmly as if it wasn't a threat.

“I'll just tell her what happened, and I wasn't jerking off to you.” I stammered, still not thinking too much about my words. She laughed at me before she spoke.

“You aren't very good at lying to women, are you Jake? If you haven't already told her, you might be past the easy confession phase. I have more than enough evidence and theories to send her down a tangent of jealousy, bitterness, and anger that you don't want to deal with. You and I both know how self-conscious she is about her little, bitty b-cups. She freed a hand briefly to tug at her bikini strap to jiggle her breasts slightly.

“Listen, Jake. I've got you by the balls. I could squeeze them, or you can let me play with them. Rosemary is going to be gone for hours, and I could use a man with your endowments to satisfy my needs. It's been so long, Jake. Please? I know you want me.” She looked at me in a way that was almost pleading but still displayed all of her confidence. I hated myself for how quickly Lily's plan seemed to be the most sensible choice of action.

I wasn't willing to take the chance to find out if she was bluffing about telling Rosemary. Lily's big breasts hung down in front of me, and each of them was as convincing to me as her golden tongue. I had always told myself that it would be easy to do the right thing in a situation like this, but when I looked into Lily's eyes I knew I was in for trouble.

“Rosemary would never do something like this. What are you doing to me, Lily?” I asked the question in a tone that betrayed my intentions to give in to her. She smiled and reached out to pull me closer by the waistband of my shorts.

“I would bet that straight-edged Rosemary doesn't get too far into cosplay, does she?” She had a satisfied smile painted on her face as she pulled down the old pair of basketball shorts I was wearing and started to rub my penis, which was mostly hard already. She enjoyed the feel of its girth in her hand as it fully hardened.

“No, she tends to stick with whatever she has on at the time,” I said as she licked the head. Her only response was a quick smile before she slid the tip between her lips. She gave me slow and gentle head on all fours, while I stood in front of her and admired the way her ass looked from my angle. She gave out cute little moans occasionally which I loved listening to while I ran my fingers through her hair. After a few moments, she sat back on her heels and indicated for me to lie down on the bed.

I pulled my shirt off while she removed her jacket and tossed it on the bed. She reached up to the tie on her bikini strap and gave me a teasing smile while she paused for effect. Any notion of guilt was banished from my mind by the anticipation she had built up. She pulled the string loose and let it fall to reveal her breasts, they were every bit as lovely as I pictured them to be and more. I was enamored with each little bump my eyes found as they explored her areolas. She was pleased by my reaction and smiled at me.

“They're a little more than you are used to I guess, huh?” She chuckled darkly as she lightly ran her fingers across her nipples, before crawling up to my crotch to continue what she started with my penis. Her warm, wet lips slipped eagerly up and down the upper portion. Her enthusiasm for the task greatly exceed anything that I had received from Rosemary in a long time. I moaned loudly, like a teenager getting his first blowjob, as she continued.

“Oh, Lily. You suck dick so much better than your sister.” I spoke loudly and without any shame for my words. Rosemary hated it when I spoke crassly during sex, but Lily seemed to love it. She paused and looked at me with fire in her eyes.

“I didn't take you for the bad-boy type, Jake. You come across as too much of a nerd at first, but you're all kinds of trouble aren't you?” She eagerly resumed her work before I could answer. While I disagreed with her assessment of my 'bad-boy' status, I wasn't going to argue with her. I grabbed the extra pillow to prop myself up for a better view as Lily worked me closer toward the best orgasm I would have in months. I could feel it coming quicker than I wanted, but my stamina was no match for her passionate effort.

I warned her of my impending orgasm so she could prepare to pull off and switch to a hand-job as I expected. She acted as if she hadn't heard me though and sped up. I told her again, loud and clear, but she continued until I started cumming in her mouth. I moaned loudly as she continued until I motioned her away with my hand. She got up to go rinse her mouth in the bathroom before coming back.

“I take it by that goofy look on your face that Rosemary doesn't let you cum in her mouth often.” She struggled slightly to get her tight shorts off while she spoke and I enjoyed every bit of it, she pulled her plain, black panties off and got into bed. She crawled on top of me until our lips met with a quick kiss, we each smiled before starting to passionately make-out. Our tongues gingerly explored each other's mouths. Rosemary and I kissed all the time, but it was nothing like this.

I moved a hand down between us and started to lightly play with her clit. She moaned quietly while we kissed. It was a cute sound that worked itself into my head like an earworm. I knew it would haunt me the next time I zoned out at work, or during a conversation with Rosemary. We broke off our kiss and she moaned quietly in my ear while I rubbed slow, wet circles on her clit. I could tell that she was getting closer to an orgasm, so I pulled my hand out and shuffled my hips down slightly so I could position myself to penetrate her.

“Please be gentle, it's been a while for me.” She sounded adorable as she spoke.

“Of course,” was my only reply. I started slowly pushing into her, centimeter by centimeter until I was all the way in.

"Oh, Jake. You're so big!” she gasped breathlessly in my ear as I pulled out and began to repeat my gentle thrusting into her. She gave me a long, passionate kiss before lifting her torso so her breasts hung above me. I stuck my tongue out to catch her nipples as she rubbed them on my face. She lifted herself and started to work her hips and pelvis a bit faster on my cock. I loved the look of her breasts as they jiggled with every little bounce. I looked over at the leather jacket and then looked back up at her with a smirk on my face.

“Put the jacket back on.” I wasn't disappointed to see her remove it earlier so she could get at her bikini top, but it seemed a shame to waste a good cosplay experience. She smiled at me and reached for it without any hesitation. Rosemary would have laughed at me for a request like that but Lily seemed excited about it, despite how hot it was getting in this little room. She zipped it up just enough so that her nipples were covered, there was a copious amount of cleavage and it drove me wild as I watched her riding me.

Soon, she started to bring her pelvis down on my thighs faster and indicated that she was close to an orgasm. I put both of my hands on her hips so I could feel the motion of her body as she finished herself off.

“Oh, Jake. I'm cumming!” Her words burned into my memory. They were pleasantly urgent as her breathing got heavy in my ear, it was a struggle to maintain my composure to avoid ejaculating inside her at the sound of that sweet voice. She slowed her pace and lowered her torso down so it rested on my chest as she basked in the last of her orgasm.

She got off and removed the jacket. She tossed it to the floor before laying next to me.

“I want to cum on your boobs,” I spoke urgently as I jerked myself off while watching her. She held her boobs together for me and offered verbal encouragement to push me over the edge.

“Cum for me, baby.” She spoke in a confident tone. I was surprised to hear her call me 'baby' but I couldn't deny my enjoyment as my semen landed on her breasts. After I was finished I took a deep breath before grabbing a towel for her and getting back on the bed.

“Wow.” Was all I could say as she cleaned herself. I spooned up behind her and held her hot, sweaty body against mine. She sighed comfortably as we relaxed into each other. I wondered if Rosemary would be more hurt by our passionate sex or the undeniable intimacy of this moment. Lily broke the silence and interrupted my thoughts.

“I know I should feel bad about this Jake, but I don't.” She tightened her grip on my arm as I held her.

“Yeah, that was great,” I spoke ambiguously. Her words rang true for me, but I wasn't ready to get into the details with her yet. I knew I would have to do right by Rosemary, but I also knew this wouldn't be the last time Lily and I ended up in each other's arms. I flexed my fingers ever so slightly into the warm flesh of her breasts and relaxed while I tried to clear my thoughts. Somewhere in the back of my mind, I could hear the voice of my inner ass-hole speak up.

'If you play your cards right, maybe you can fuck both sisters on the same day.' I smiled to myself at this wicked thought and held Lily a bit tighter, as I pondered how much longer I had until Rosemary came back home from work.