Your brother's accountability for this accident could vary depending his fault regarding this accident. The police should be contacted for every accident. And, this accident is no different. They will determine their level of involvement. They may determine fault for this accident. Now, the penalties for driving without a driver's license varies from state to state. And, depending on the state in which he resides and was driving, your brother may be held accountable for driving without insurance. The penalties for this, too, also varies from state to state. He can follow this link to learn about his state's insurance laws.