There are two ways you can have a sister-in-law.
No relation...lol
No. The sister is a relation, and her husband is an in-law. The husband's brother is no biological relation either. Therefore, the great granddaughter of the husband's brother is not a relation.
He is of relation as a cousin-in-law.
Your cousin-in-law.
There is none.
Your husband's grandniece is your grandniece-in-law.
He is technically no relation, as you do not share a common ancestor. He is your husband's first cousin once removed.
You are not related to your cousin's husband. He would simply be "My cousin's husband."
Your daughter's husband is your son-in-law.
Your husband and your aunt are not related to each other.
The brothers of your husband are your brothers-in-law.
He is you grandfather in law