As I understand it, in the Sephardic world not long ago, the marriage contract would have a steep penalty clause if he took a wife beyond the first one without her permission.
And as I understand it, in the Sephardic world till today, yibum is preferred over chalitza, i.e. the best thing is to marry the widow.
So suppose Hayim marries Mazal, and their contract has a penalty clause. Then Hayim's brother dies childless, so Hayim is supposed to marry his brother's widow. Mazal says she doesn't want another wife around.