Md. Code, Insurance § 15-402

(a) This section applies to:

(1) each individual or group health insurance policy that is issued in the State; and

(2) each contract that is issued in the State by a nonprofit health service plan or a health maintenance organization.

(b) (1) Notwithstanding any limiting age stated in a policy or contract subject to this section, a child, grandchild, or individual for whom guardianship is granted by court or testamentary appointment shall continue to be covered under the policy or contract as a dependent of an employee, member, or other covered individual if the child, grandchild, or individual under guardianship:

(i) is unmarried;

(ii) is chiefly dependent for support on the employee, member, or other covered individual; and

(iii) at the time of reaching the limiting age, is incapable of self–support because of mental or physical incapacity that started before the child, grandchild, or individual under guardianship attained the limiting age.

(2) A child, grandchild, or individual under guardianship who is covered under this section shall continue to be covered while remaining unmarried, dependent, and mentally or physically incapacitated until the coverage on the employee, member, or other covered individual on whom the child, grandchild, or individual under guardianship is dependent terminates.

(c) To be eligible for coverage under this section:

(1) a grandchild must be a dependent, and in the court–ordered custody, of the employee, member, or other covered individual; and

(2) an individual must be a dependent and in the custody of the employee, member, or other covered individual as a result of a guardianship, other than a temporary guardianship of less than 12 months duration, granted by court or testamentary appointment.