Unfortunately, as the registered owner of the vehicle, you are liable for damages from an accident caused by your sibling driving your car. Your liability would include the property damage and personal injury claims of the occupant or occupants of the other vehicle not at fault in the accident.If you had auto insurance, refer the matter to your auto insurance company.  If the case is settled with the other party, NO lawsuit is filed.  If the case is NOT settled with the other party and a lawsuit is filed against you, your auto insurance company will provide you with an attorney at no cost to you.You can also sue your sibling to recover the amount of a judgment against you.  You can also sue your sibling for conversion for driving your car without your consent.  Conversion is the unauthorized assumption of the right of ownership over your personal property.  Conversion is any unauthorized act which deprives the owner of his or her property permanently or for an indefinite time.  Conversion is a civil case (lawsuit) for theft.  You would file only one lawsuit against your sibling with separate causes of action (claims) for negligence (for the accident) and conversion (for taking your vehicle).