Nicholas thought about Duke Romanov's wife and assumed the woman must be not in her right mind. Or she could be just as vile as the dark duke. Like beget like, doesn't it? Only a wicked woman would marry a wicked duke.
It was a different story if she was forced into the marriage. He could imagine that this was not something beneath the dark duke, forcing a woman to marry him.
Or, she might be a poor woman who needed the duke's money to survive. Being pragmatic was not a sin. Everybody needed money to eat. Nicholas could only feel sorry for the woman if that was the case.
He heard how the duke was ugly and disfigured that he needed to cover his face with a mask just to go out. So, people wouldn't be repulsed at seeing him. His wife would be forced to live with him in that state every day throughout the marriage.
