If you have a child, chances are you have already or will in the future sign your child's driver's license application as a sponsor. Wis. Stat. §343.15 mandates that any person under the age of 18 (with a few exceptions such as those with no living parent) who wishes to apply for a driver's license must have a sponsor. By sponsoring a driver's license, a sponsor agrees to be held jointly and severally liable for damages caused by negligent or willful misconduct of the sponsored driver. In most cases if your child is added to your insurance policy, you may have less to worry about (from a financial standpoint). However, if your child has their own car and insurance policy, you may want to review both of the policies.