Most employers generally are aware of their obligations under the Family and Medical Leave Act to grant leave to employees to care for family members. However, FMLA narrowly limits the definition of family member to a "spouse, or a son, daughter or parent, of the employee, if such spouse, son, daughter or parent has a serious health condition." This definition may appear self-explanatory, but it is further restricted by the U.S. Department of Labor's interpretive regulations, which set forth additional criteria for determining whether the requested leave is indeed needed to care for the family member.

For the most part, the term "family member" adheres to its ordinarily accepted meaning, but there are exceptions.

FMLA defines "parent" as the biological parent of an employee, or an individual who stood "in loco parentis," or acted as a parent to an employee, when the employee was a minor. The definition does not include a parent-in-law or grandparent unless the individual stands "in loco parentis" to the requesting employee.