Parental liability only applies to your minor or underage children. The age of majority is the age at which a minor, in the eyes of the state law, becomes an adult. This age is 18 in most states. In a few other states, the age of majority is 19 or 21. You may want to check your state's legal age of majority laws. A minor is considered a resident of the same state as the minor's custodial parent or guardian. If your minor child spends time with two parents in two different states, each parent is responsible for the child's actions while in their care.