Your sister's daughter is your niece and you are either her aunt or her uncle. The English language has no term for your niece's husband, other than calling him "niece's husband."
Your husband's cousin's sister is also your husband's cousin. You are not related to your husband's cousin.
sister in law
Real sister, half sister, or step sister
Your brother would call your husbands sister by her first name. Or, "my (sibling's) sister in law.
sister in law.
Your Sister-in-law
Cousin in Law
Your sister's sister is your sister.
you call her your daughter's husband's sister
Mom
No relation whatsoever. You will be an aunt or uncle to your sister's child and your brother-in-law's sister will be the child's aunt, but that's as close as it gets.
brother in law