There is none, as there is no actual relationship.
Your brother to her would be a brother-in-law.
Your brother's wife is your sister-in-law. The English language has no relationship term for the brother of your sister-in-law. He is not considered to be related toyou, although he is your brother's brother-in-law.
Brother-in-law
You brother is your grandchildren's great uncle or granduncle.Your grandchildren are your brother's grandnieces and grandnephews
Your wife's brother is your brother-in-law.
Your brother-in-law is either the husband of your sister or the brother of your spouse.Where your brother-in-law is the husband of your sister, there is no relationship name in the English language to describe his brother's relationship to you. However, in that situation your brother-in-law's brother is your sister'sbrother-in-law.Where your brother-in-law is the brother of your spouse, his brother is also your brother-in-law.
You would be 2nd cousins, assuming that the brother's wife's granddaughter is also the brother's granddaughter. If the granddaughter is not the granddaughter of the brother, there is no relationship.
He is brother your brother in law.
your son is your brother's nephew, and your brother is your son's uncle
Unless your brother-in-law's brother is your husband, there is no direct relationship.
Your grandfather's brother is your great uncle