If your brother-in-law is your wife's brother, then his sister is either your wife or one of her sisters and thus your sister-in-law.
If your brother-in-law is your husband's brother, then his sister is your sister-in-law.
If your brother-in-law is the husband of your sister, then his sister is not related to you, but is your sister's sister-in-law.
I call them my uncles
a cow
Nieces.
Chachi
Bob No bog
Your cousin in law
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.
Your parent's brothers are your uncles and your parent's sisters are your aunts.
Yes if you will mean that uncles posses something. Examples: uncles' houses (the houses of uncles) uncles' children (the children of uncles)
Your uncle/aunt's son/daughter is an adult and you are still small, your uncle/aunt's daughter had a child, and that child will call you uncle. Uncles/aunts are your dad/mom's siblings.
Cousin. Your parents brothers and sisters are aunts and uncles. and the aunt and uncles children are your cousins.
Chiron, Bythos, Aphros would be uncles by Kronos and Philyra; by Kronos and Rhea her uncles are Poseidon and Hades, both brothers of Zeus are her uncles; on her mother's side she did not have uncles.