She is your Great Aunt in law!
Your granddaughter's husband might be called your grandson-in-law, although the term is rarely used. Hissister is your granddaughter's sister-in-law, but is not related to you.
Your father's brother is your uncle. Your uncle's wife is your aunt (and your father's sister-in-law). Her sister is not related to you or to your father, but is your uncle's sister-in-law.
Your mothers' uncles' daughters' husbands' brother is in no way related to you. 1. Your mother's Uncle is your Great Uncle. 2. His daughter would be you and your mother's cousin. 3. Her husband would be your cousin's husband - no relation to you. 4. Therefore, that makes your cousin's brother-in-law no relation to you.
There is no relation between you, and your biological Uncle's wife's sibling's daughter. Your Uncle's wife is technically an "Aunt in law", though as routine courtesy is simply called "Aunt". Her brother/sister, if your family and her family are that close, could be regarded as an "Uncle/Aunt in law", as a stretch. Thus the daughter of him/her could be thought of as a "cousin in law" to you. But this is all a matter of courtesy, there is no biological or legal relation.
Your uncle's wife is your aunt.
Your mom's brother's wife would be your uncle's wife, or your aunt-in-law.
Your uncle would be your sons great uncle. Normally your Son would also call him 'Uncle .... '
Your sister-in-law is either the sister of your spouse or the wife of your brother. In either case, her children are your nieces and nephews and you are their aunt (if you are female) or their uncle (if you are male).
Yes, your wife's nephew is your nephew because you are his uncle.The aunt and uncle relationship is different from many other family relationships because you can become an aunt or uncle simply by marrying someone whose sibling has a child.Your parent's brother is your uncle and his wife is always your aunt, even though you have no genetic relationship. She is not your aunt-in-law.
Your uncle's sister is your aunt, or possibly your mother.
His relationship to you is brother-in-law.
No. Cousins are people who are descended from some common ancestor.