Your brother-in-law would be the brother of your wife or husband, making them siblings. Their mother would be your mother in law.
What Relation Is My Brother-in-law's Mother To Me?
My sisters husband is my brother in law but his mother in no relation to me at all. She is simply my sisters mum in law.
My husbands brother, on the other hand , is also my brother in law BUT his mum is obviously my mother in law and so it depends which type of brother in law you refer to which surely must be the first kind.
My husbands brother, on the other hand , is also my brother in law BUT his mum is obviously my mother in law and so it depends which type of brother in law you refer to which surely must be the first kind.