The Wrong Vow: An affair with my sister's fiance.

I shouldn't have been watching him. Not the way I was. Not from the hallway outside my sister’s bedroom as he sat alone in the kitchen, shirt unbuttoned, tie loosened, sipping the last of the wine we’d opened to celebrate their engagement. But I was watching him. Like a sinner watches fire—knowing it will burn but unable to turn away. Liam Carter. My sister’s fiancé. And the man I couldn’t stop thinking about. “I know you’re there,” he said without looking up. Shit. I stepped out of the shadows, trying to play it cool. “You always this charming after midnight?” He smirked. “Only when the bride’s sister is lurking in the hallway like a ghost.” I rolled my eyes, but my skin flushed. “I wasn’t lurking.” “You were.” I crossed my arms. “And what if I was?” He finally looked up at me. And for a second, everything went still. His eyes dragged over me like a slow caress. It wasn’t the first time he looked at me like that. It wouldn’t be the last. “You shouldn’t look at me like that,” I said. “Then stop looking back.” Silence. My heartbeat was a slow, painful thud in my chest. I hated how aware I was of him—his voice, his scent, the way he leaned back in his chair like he owned the room, the house, the very air I breathed. “She’s your sister,” he said, but his voice lacked conviction. “And you’re going to marry her.” “I know.” He stood up slowly, glass in hand, eyes never leaving mine. He didn’t touch me. He didn’t have to. Every inch of space between us was already charged. “Goodnight, Amelia.” He walked past me, and I didn’t move. I couldn’t. Because deep down, I already knew— This wasn’t the end. It was the beginning. Two Days Later I avoided him like he was fire and I was made of gasoline. Which wasn’t easy when he was practically living at our family’s house now, helping Claire finalize wedding details, charming our parents, smiling that too-perfect smile that made me want to slap him—or kiss him. I stayed out late, came home early, found excuses to be anywhere but around him. But I could still feel that night like it had been stitched into my skin—the wine on his breath, the way his eyes had lingered on my lips, the sound of my name in his mouth. It was poison. And I was already addicted. “Where’s the seating chart?” Claire asked, snapping me back to reality as we sat around the dining table, covered in bridal chaos—flowers, sample menus, fabric swatches, and way too many post-it notes. I reached for the stack beside me, accidentally knocking over a silver pen. Liam picked it up and handed it to me, fingers brushing mine. Too long. Too soft. Too intentional. I didn’t look at him. “Thanks,” I muttered. “You okay?” Claire asked, watching me. “Yeah. Just tired.” A lie. “Maybe lay off the late nights,” Liam said casually, sipping his coffee without meeting my eyes. Claire laughed. “She’s always been the wild one.” I forced a smile. “And you’ve always been the golden child.” We both laughed, but Liam didn’t. He was looking at me now, really looking. Like he could see the guilt crawling under my skin. “I should go,” I said quickly, grabbing my phone. “But you just got here,” Claire protested. I stood anyway. “I’ve got errands. I’ll be back later.” I didn’t wait for a reply. I was halfway to my car when I heard footsteps behind me. “Amelia—” I turned. “Don’t.” Liam stopped. “I wasn’t going to say anything.” “You don’t have to. You keep looking at me like you already did.” He ran a hand through his hair. “We need to talk.” “No, we don’t. You’re marrying my sister, remember?” His jaw tightened. “And you’re acting like I’m the only one who crossed a line.” I flinched. Because he was right. But I didn’t say that. Instead, I said, “You’re a coward.” “And you’re a liar if you say you didn’t feel anything that night.” Silence hung between us, heavy and charged. “Just—stay away from me,” I said, voice breaking. But even as I said it, I didn’t move. Neither did he. And that scared me more than anything else. One Week Later Weddings make people insane. Or maybe it was just this wedding. My mother was barking orders like a general in a war zone, my sister was micro-managing the flower delivery like it was a hostage negotiation, and Liam— Liam was standing in my bedroom. “What the hell are you doing in here?” I snapped, slamming the door behind me. He turned, completely unfazed. “Your mom asked me to find the guest list. Said it might be in your room.” “And you just walked in?” “I knocked. You didn’t answer.” “Maybe because it’s my room?” His eyes narrowed. “You’ve been avoiding me.” “Damn right I have.” He stepped closer. “I told you we needed to talk.” “No,” I said, backing up. “You said you needed to talk. I need to forget any of this ever happened.” He reached out, but didn’t touch me. “I can’t stop thinking about you.” “Don’t.” “I’m serious, Amelia. That night—” “Was a mistake,” I interrupted. “A horrible, selfish, disgusting mistake. And if you ever cared about Claire, or about me, you’ll leave right now.” “You really think this is just lust?” “What else would it be?” “I don’t know,” he said quietly. “But it doesn’t feel like nothing.” My voice broke before I could stop it. “She loves you.” He nodded slowly. “I know.” “And you’re supposed to marry her.” He didn’t respond. That silence was more dangerous than anything he could’ve said. “Get out,” I whispered, because I didn’t trust myself. He turned to go. But at the door, he paused. “You’re right, Amelia. It was a mistake. But don’t pretend you didn’t feel it too. That’s the worst kind of lie.” Then he was gone. And I was alone in the storm he left behind. Two Days Later Claire was humming. That was never a good sign. She only hummed when she was obsessively happy—or hiding something. And today, she was floating around the living room, wedding binder in hand, like she hadn’t a care in the world. “You okay?” I asked cautiously, sipping my coffee. She looked up and smiled. “Never better.” Liar. I watched her for a moment, noting the edge behind her smile, the way her fingers clutched the binder a little too tight. Something was wrong. But instead of saying it, I waited. Claire closed the binder and sat beside me. “So... I talked to Liam last night.” My heart dropped like a stone in my chest. “Yeah?” “Yeah.” Her tone was light, but her eyes were sharp now, watching me carefully. “He seemed... distracted. Off.” I forced a shrug. “Maybe it’s the wedding stress?” She tilted her head. “Is that all?” I nodded. Too fast. Too obvious. Claire reached for my hand. “Amelia, can I ask you something? And I want you to be honest.” I swallowed. “Okay...” “Do you like him?” I blinked. “What?” She let out a quiet laugh, but it didn’t reach her eyes. “I mean, it’s obvious he likes you. He looks at you like—” She stopped, shaking her head. “God, maybe I’m crazy. Maybe it’s just my anxiety. I don’t know.” “You’re not crazy,” I said, and instantly regretted it. Her eyes sharpened. “Then what am I seeing?” I couldn’t breathe. Couldn’t lie. But I also couldn’t say it. Couldn’t crush her like that. “I think... he’s just nervous,” I said quietly. “You know how guys get. Cold feet, stress, big commitment.” Claire nodded slowly. “Yeah. Maybe.” But I could tell she didn’t believe me. I stood up quickly. “I should go. I promised Jenna I’d meet her for lunch.” I grabbed my bag and made it to the door before she said, “You’d tell me, right? If something was happening?” I froze. My back to her, I forced the lie out on trembling lips. “Of course I would." Later That Week Claire was glowing. She twirled in front of the mirror in her wedding dress, lace cascading around her like a fairytale spun into silk. The boutique smelled of roses and champagne, and my stomach was in knots. “What do you think?” she asked, spinning toward me, eyes shining with hope. I swallowed the lump in my throat. “You look... breathtaking.” She beamed. “Really? Not too much?” “No. It’s perfect,” I said, and meant it. The dress was perfect. The moment was perfect. And I hated how much I wanted to ruin it. “You know,” Claire said, stepping off the platform and linking arms with me, “I always pictured this with you by my side. Ever since we were little, playing dress-up with Mom’s old veils.” I smiled weakly. “You always picked the prince too fast.” “And you always wanted to run the kingdom.” We laughed, and for a moment, it felt like the way things used to be—before Liam, before secrets, before guilt wrapped itself around my heart like barbed wire. Claire pulled away and turned serious. “I know I’m a little...intense. I can be controlling, and you’ve been amazing through all of this. I’m so glad you’re here.” The words were a dagger to the chest. I didn’t deserve her kindness. Her trust. “I mean it,” she said, hugging me tight. “You’re my maid of honor, but more than that—you’re my best friend.” My best friend. My sister. And I was sleeping with her fiancé. I squeezed my eyes shut as she held me, breathing in the warmth of a moment I didn’t deserve to be in. “I love you, Amelia.” “I love you too,” I whispered, the lie tasting like ash in my mouth. And for the first time, I wondered— What would happen if I told her the truth?