Just because the player wants to be a harem protagonist does not mean the companions will meekly accept their roles as notches on a bedpost. Shadowheart, for instance, brushes off Wyl's flirtations with the given reason that she knows he has flirted with Laezal and she does not want to play second fiddle. "Poly" aside, if you want to bring real life into this, adultery is often the death knell of a relationship, no matter how much the adulterer may wave their hands and try to "resolve misunderstandings."