You can't do anything to force him to insure you. You are unfortunately mistaken as to the law--you are not "supposed" to be insured until the age of 26; rather, the law gives parents the right, but not the obligation, to keep their children on their insurance until age 26 as a way to get the children lower-cost insurance. However, any parent, unless subject to some court order to the contrary from child support or custody proceedings, is free to not insure their adult children.As an adult, your option to get health insurance is the same as that of every other adult: you may purchase your own insurance.