; or (B) in the case of an unmarried employee, an unmarried adult person who is in a committed, personal relationship with the employee, is not a domestic partner to any other person, and who is designated to the employer by such employee as that employee’s domestic partner. (21) Grandchild The term grandchild means the son or daughter of an employee’s son or daughter. (22) Grandparent The term grandparent means a parent of a parent of an employee. (23) Parent-in-law The term parent-in-law means a parent of the spouse or domestic partner of an employee. (24) Sibling The term sibling means any person who is a son or daughter of an employee’s parent. (25) Son-in-law and daughter-in-law The terms son-in-law and daughter-in-law , used with respect to an employee, means any person who is a spouse or domestic partner of a son or daughter of the employee. (26) Aunt or Uncle The term aunt or uncle of the employee , means the sister or brother of an employee’s parent. (27) Any other individual related by blood or affinity whose close association is the equivalent of a family relationship The term any other individual related by blood or affinity whose close association is the equivalent of a family relationship means any person with whom the employee has a significant personal bond that is or is like a family relationship, regardless of biological or legal relationship. . (2) Inclusion of adult children and children of a domestic partner Section 101(12) of such Act ( 29 U.S.C. 2611(12) ) is amended— (A) by inserting a child of an individual’s domestic partner, after a legal ward,