After Discovering His Betrayal, I Married His Rival

The penthouse sparkled under the glow of crystal chandeliers, casting prismatic light across the marble floors of the Summers estate. I smoothed the silk of my champagne-colored gown, my fingers trembling slightly as they brushed over my still-flat stomach. Our baby. Alexander's and mine. The secret knowledge warmed me from within, a tiny ember of joy I couldn't wait to share.

"Tonight's the night," I whispered to my reflection in the gilded mirror of the powder room. My cheeks were flushed with anticipation, eyes bright with promise. At twenty-three, I was finally ready to announce my choice – though it had never truly been a choice at all. My heart had belonged to Alexander Sterling since we were teenagers, growing up together in this very penthouse.

I practiced the words silently: "I choose Alexander." So simple, yet they would change everything. The arrangement my parents had created when they took in the three boys as wards had always seemed like a fairytale to me – that one day, I would marry one of them to unite our family businesses. That Alexander and I had fallen deeply in love seemed like destiny's blessing on the arrangement.

The party for Alexander's thirtieth birthday was in full swing as I emerged from the powder room. Manhattan's elite mingled throughout our Upper East Side penthouse, champagne flutes clinking, laughter rising and falling like music. My father caught my eye from across the room and nodded encouragingly. He knew what tonight meant.

"Have you seen Alexander?" I asked a passing waiter, who gestured toward the library.

"I believe Mr. Sterling went that way with his brothers, Miss Summers."

Perfect. All three brothers together – Alexander, Gabriel, and Sebastian. I could make my announcement to them privately first, before sharing with the guests. And then, when Alexander's face lit up with joy, I would whisper in his ear about the baby.

The hallway leading to the library was quieter, the sounds of the party fading behind me. I slowed as I approached the heavy oak doors, hearing Victoria Walsh's distinctive laugh from within. Victoria, their childhood friend from the Hamptons. Something about her had always made me uneasy – the way her eyes followed Alexander, perhaps, or how the brothers seemed to transform in her presence.

I reached for the door handle but paused when I heard my name.

"Poor Isabella," Victoria's voice dripped with mock sympathy. "She actually believes you love her, Alexander. It's almost cruel how convincing you've been."

My hand froze on the handle. The clinking of ice against glass – someone pouring drinks.

"We've all been convincing," came Sebastian's voice, lower and tinged with amusement. "That was the point of the game, wasn't it?"

Game? I stepped back from the door, my heart suddenly hammering against my ribs. Instead of entering, I moved silently to the side, where a gap in the bookshelves allowed me to see into the room without being noticed.

Victoria stood by the bar cart, pouring amber liquid