Michigan Compiled Laws, Chapter 500. Insurance Code of 1956 § 500.2264

Sec. 2264. Any contract or insurance policy delivered on or after July 12, 1966 in this state providing for hospital care or reimbursement for the care of the policyholders and dependents that provides for termination of dependent coverage at a specified age does not apply to an unmarried child of the policyholder who is incapable of self-support due to developmental disability or physical disability, and who is dependent upon the policyholder for support and maintenance, if the policyholder submits satisfactory proof of the dependent's incapacity to the insurance carrier not later than 31 days after the attainment of the age limit by the dependent child.