Do sister-in-laws count as immediate family?

Answer 1

sometimes, if you are close to that person, however, if you aren't then no --- It depends on the cultural customs of your and their families.

Some cultures have extremely close extended loyal family structures.

Other cultures have even immediate family members living

far apart with only occasional contact. (Compared to the statistical mean)

Answer 2

That will depend greatly on the situation. For purposes of some benefits (for example, discounts from automakers for an employee's mother-in-law) she is considered immediate family.

Most hospitals would consider her immediate family, particularly if she is with the spouse.

In many legal matters, she is not considered immediate family.