I was just trying to prevent the breakup of the main characters

I was just trying to prevent the breakup of the main characters summary:

In a romance novel full of shoveling and misunderstanding, she possessed Namjoo's younger sister. Fallen in the novel, I took off my feet for the frustrating main couple, but on the day of their engagement , the main characters declared their breakup! And at the center of it was the heroine's older brother, 'Aiberg Raphael'. The monster duke, aiberg was quite a 'siscon'... … . In order to get rid of 'Siscon', wouldn't it be reasonable to just do it? “What is the Duke's ideal type?” “A woman with red hair and eyes resembling blazing fire, and who will not be discouraged by whoever stands before me. Ah, when I say this... … You look like my ideal type.” I was just trying to prevent the breakup of the main characters, but did I cheat on the female protagonist's brother without knowing it?