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.
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He would call your aunt his great aunt. In informal situations, great aunts are sometimes called, simply aunt.
Your grandfather's brother is your Great Uncle.
The relationship of the sibling of your sister-in-law or brother-in-law to you does not have a name in English. You could call them your brother- or sister-in-law if you want, or you can call them the brother or sister of your brother- or sister-in-law.
Oba-san = aunty (formal) it's mostly used for more elderly aunts or distant (less familiar) aunts. Oba= aunt (normal) Changing it to 'chan' makes it more casual.
Your aunts and uncles are the sisters and brothers of your parents. So they are "blood related." But you also call the husband of your mother's sister your uncle, and he is not "blood related." So aunts and uncles are not always really related to you.