You are her niece or nephew (niece if female, nephew if male) and she is your aunt.
sister-in-law
You are his uncle, he is your nephew.
A reflective relation is one where the relation holding between A and B implies that the relation also holds between B and A 'sibling' is a reflective relation. A is B's sibling implies that B is A's sibling. In contrast, 'sister' is not reflective, A is B's sister does not imply that B is A's sister (for B might be male).
Hailie Jade Mathers doesnt have a bioloical sister but kim had a daughter from her previous marriage and eminem and kim had adopted their niece Lainie or Alaine so her cousin is her sister and a step sister
There is none.
They were brother and sister.
she would be your sister in law
Your sister and your wife are sisters-in-law to each other.
Real sister, half sister, or step sister
sister in law.
The English language makes no distinction between an elder sister and a younger sister, or their children. Your sister's son is your nephew.
Your sister's sister is your sister.