Does an expired drivers license invalidate liability insurance?

While a driver is expected to have a valid license when they purchase insurance, once the policy is in force, the insurance company should pay for any accident to involves the insured driver.  The insurance company is responsible to be sure the driver is still eligible for the insurance and if they have not taken any action then the policy remains in force.

There may be some special policies that say the insurance is invalid if there is not a licensed driver involved.  Your brother needs to talk to his insurance agent to see if there is any special exclusion.  He also needs to go to the Dept of Motor Vehicles and renew his license immediately,if he has not already done so.  A lapsed license is not usually an intentional action, often times it is just an oversight so no criminal intent is indicated.