Under the Family and Medical Leave Act (FMLA), the status of acting with day-to-day responsibilities to care for and financially support a child, without necessarily having a biological or legal relationship to the child (29 C.F.R. § 825.122).

The definition of parent for certain purposes under the FMLA includes those who stood in loco parentis to the employee when the employee was a child (29 C.F.R. § 825.122). For more information, see FMLA Employer Coverage, Employee Eligibility, and Qualifying Reason Checklist: Family Definitions. For example, an employee may be eligible to take FMLA leave to care for an aunt with a serious health condition, if that aunt was responsible for the employee's day-to-day care when the employee was a child (see DOL: Fact Sheet #28C).

Similarly, the definition of son, daughter, and child for certain purposes under the FMLA includes a child of a person standing in loco parentis (29 C.F.R. §§ 825.122 and 825.126). For more information, see FMLA Employer Coverage, Employee Eligibility, and Qualifying Reason Checklist: Family Definitions. For example, an employee who will co-parent a same-sex partner's biological or adoptive child may be eligible for FMLA leave for the birth or adoption of the child (see DOL: Fact Sheet #28B).

For more information, see Practice Notes, Family and Medical Leave Act (FMLA) Basics and Pregnancy and Parental Leave: The Family and Medical Leave Act.