(12) Dependent. The term dependent means a child (as defined in section 152(f)(1) but excluding a stepson, stepdaughter or an eligible foster child (and excluding any individual who is excluded from the definition of dependent under section 152 by operation of section 152(b)(3))) of an employee who has not attained age 26. A child attains age 26 on the 26th anniversary of the date the child was born. A child is a dependent for purposes of section 4980H for the entire calendar month during which he or she attains age 26. Absent knowledge to the contrary, applicable large employer members may rely on an employee's representation about that employee's children and the ages of those children. The term dependent does not include the spouse of an employee.