The Contract Marriage

The day before her wedding, she witnessed her boyfriend, whom she loved for nine years, having an affair with his big brother's fiancée. He was even plotting to marry his future sister-in-law as she's carrying his baby.
While this disgusting truth broke her heart, a reserved man stepped into her life. He offered a sophisticated solution.
"Marry me instead, so my shameless brother and fiancée will have to call you Sister-in-law for rest of their life. Agree?"
It didn't take long, she took his offer. But she could never think that this man is precisely the opposite of what he claimed to have been crippled, impotent and infertility for years instead he wants her, every minute...