What family legal documents do I need to board a Royal Caribbean cruise ship?

Should the last names of the parent and minor child travelling with them differ, the parent is required to present the child's valid passport and visa (if required) and the child's birth certificate (original, a notarised copy or a certified copy). The name of the parent(s) and the child must be linked through legal documentation.

Adults who are not the parent or legal guardian of any minor child travelling with them are required to present the child's valid passport and visa or the child's birth certificate (original, a notarised copy or a certified copy) and an original notarised letter signed by at least one of the child's parents. Adults who are not the parent or legal guardian of a minor travelling with them must present an original notarised letter signed by the child's parent(s), authorising the adult to take the child on the specific cruise, supervise the child and allow emergency medical treatment to be administered. If a non-parent adult is a legal guardian, the adult must present a certified certificate of guardianship with respect to the child.