A woman can use this to describe the brother of the man that she is going to marry. When a man is going to be married, his future wife can use the term 'fiancé' to describe him. For example I am getting married in July (for real) and so my girlfriend can now say that I am her fiancé. Fiancée is the female version of the same thing. So I can now say that my girlfriend is my fiancée. So if she was to say 'fiancé's brother', she would mean my brother. I hope that helps.

A woman can use this to describe the brother of the man that she is going to marry. Once she is married she will call him her 'brother in-law'.

A woman can use this to describe the brother of the man that she is going to marry. Once she is married she will call him her 'brother in-law'.