Escaping My Contract Husband, Finding His Step Brother

The night of my engagement party, I discovered my future contract husband was cheating with my sister. I was angry and broken all at once. So when I found his so called useless stepbrother, I married him instead. But why was he the one begging me to come back afterward? And who would have thought that his useless stepbrother would turned out to be the best man I'd ever met.