The Broken Vows (The Windsors #4) by Catharina Maura

Description

She was his first love, his first heartbreak, and his only regret.

Zane Windsor always loved the way Celeste Harrison’s eyes light up when he infuriates her. It just took him years to realize that what he felt for his childhood rival wasn’t hatred.

When they begin working for their family businesses, competing on a larger scale than ever before, he decides he wants it all with her — and what Zane Windsor wants, he gets.

Zane and Celeste discover just how thin the line between love and hate truly is, falling harder than either of them thought possible…

…until an unexpected tragedy leaves them wondering if any of it was ever real at all.

Led by a desire for revenge, Zane brings Celeste’s company to the brink of bankruptcy, leaving both of their grandparents no choice but to intervene.

The Windsors and Harrisons agree to a merger — on one condition: Zane and Celeste must marry each other.