By marriage yes as his thought of as distant uncle or uncle in law.
And if ever intorduce him to someone outside family or talk about him you can just say his my uncle without going thought wifetales.
Your aunt's husband is usually considered to be your uncle, but his brother is not related to you, so the brother's daughter is not related to you either.
Your brother's aunt is probably your aunt as well.
When your aunt is your aunt because she married your father's brother, her mother is not related to you.
She is your great aunt by marriage. She could also be your grandmother, if your father's aunt's brother is your grandfather.
Your father's brother's wife is your aunt, but her cousins and their children are not related to you.
Your aunt is either the sister of one of your parents or the wife of the brother of one of your parents. If your aunt is the sister of a parent, her mother is your grandmother. If your aunt is the wife of a brother of one of your parents, her mother is not related to you.
If your aunt is the sister of one of your parents, her husband's brother (her brother-in-law) is not related to you. If your aunt is the wife of a brother of one of your parents, then her husband's brother (her brother-in-law) is either your father or another one of your parents' brothers.
Your brother's daughter is your niece. You are her aunt (if you are a woman) or her uncle (if you are a man).
Your brother's son is your nephew. If you are female you are his aunt. If you are male you are his uncle.
Your mother's brother is your uncle and his wife is your aunt.
Your brother's sister is your daughter's aunt, and your daughter is your brother's, and his sister's, niece.
It depends on the actual relationship. It is possible for your aunt's husband's brother to be your father. (She would be an aunt by marriage.) If your aunt is the actual sibling of one of your parents, then, yes, because he is not related to you "by blood ."